@article{gautam_kumar_tafreshi_pourdeyhimi_2024, title={A simple approach to simulate corona-charged electret filters}, volume={176}, ISSN={["1879-1964"]}, url={https://doi.org/10.1016/j.jaerosci.2023.106293}, DOI={10.1016/j.jaerosci.2023.106293}, abstractNote={This paper presents a novel computational model devised to simulate how different ways of corona-charging a fibrous filter can impact its aerosol collection efficiency. The model assigns different bipolar charges to the fibers in the media based on how the corona-generated negative ions impact these fibers they travel from the corona needles towards the grounded surface underneath the media. The charge assignment process is based on observations made from simulating the electrohydrodynamic field around the corona needles. With the fibers virtually charged, the trajectory of positively and negatively charged aerosol particles, ranging in size from 30 to 500 nm, were simulated across the filter thickness to quantify the effect of fiber charge distribution on the filter efficiency. The performance of our virtual filter was found to be better when it was exposed to the corona ions on both the face and back sides. More interestingly, it was found that the filtration efficiency of the filter was dependent on the order by which its face and back sides were charged. The filter was observed to capture smaller particles (less than 150 nm) more efficiently when it was first charged on the face side and then charged on the back side. The opposite effect was observed when the charging order was reversed. This difference in filtration performance was found to arise from the differences in the solid volume fraction of the filter across its thickness.}, journal={JOURNAL OF AEROSOL SCIENCE}, author={Gautam, S. and Kumar, A. and Tafreshi, H. V. and Pourdeyhimi, B.}, year={2024}, month={Feb} }
 @article{gautam_kumar_tafreshi_pourdeyhimi_2024, title={Designing Multi-Layer electret filters via numerical simulation}, volume={286}, ISSN={["1873-4405"]}, url={https://doi.org/10.1016/j.ces.2023.119680}, DOI={10.1016/j.ces.2023.119680}, abstractNote={The deposition of neutral and charged particles inside an electrostatically charged filter can affect its performance by decreasing its ability to capture additional particles and by increasing its pressure drop. The particle-loaded behavior of a composite filter comprised of three fibrous layers is studied in this paper using a macroscale simulation approach. Each of these fibrous layers were assumed to have fibers with the same amount of charge but different charge polarities of only unipolar positive, only unipolar negative, or only bipolar. The charged layers were stacked on top of one another in three different configurations with respect to the flow direction and their filtration efficiency and pressure drop were compared during particle loading with neutralized particles (having the Boltzmann equilibrium charge distribution), singly-charged particles, and neutral particles. Our simulations revealed that placing the bipolarly-charged layer downstream of the unipolarly charged layers helps to lower the negative impact of particle deposition on pressure drop and filtration efficiency of the resulting composite filter. This study introduces a design tool, which can be used to optimize the configuration of a composite filter to enhance the particle capture efficiency and minimize pressure drop.}, journal={CHEMICAL ENGINEERING SCIENCE}, author={Gautam, S. and Kumar, A. and Tafreshi, H. V. and Pourdeyhimi, B.}, year={2024}, month={Mar} }
 @article{atri_kumar_gautam_tafreshi_pourdeyhimi_2024, title={Microscale modelling of electret filters using disordered 2-D domains}, volume={431}, ISSN={["1873-328X"]}, url={https://publons.com/wos-op/publon/63528871/}, DOI={10.1016/j.powtec.2023.119094}, abstractNote={This paper reports on a computational study about the impact of fiber dipole orientation on particle collection efficiency of a bipolarly charged filter. The simulations were carried out using ANSYS software in a series of 2-D geometries comprised of randomly distributed fibers. The simulations were enhanced with in-house subroutines to incorporate Coulomb and dielectrophoretic forces in calculating particle trajectories and thereby simulating filter efficiency. The highest and lowest efficiencies were observed for dipole orientations that were perpendicular and parallel to the airflow direction, respectively. The simulation results were also compared with the predictions of the popular semi-empirical correlations from the literature and good general agreement was observed, without the need for any empirical correction factors. In addition, it was observed that the predictions of the semi-empirical correlations better agreed with the simulation results obtained for media comprised of fibers with random dipole orientations when challenged with neutralized particles.}, journal={POWDER TECHNOLOGY}, author={Atri, S. and Kumar, A. and Gautam, S. and Tafreshi, H. and Pourdeyhimi, B.}, year={2024}, month={Jan} }
 @article{raza_he_tafreshi_liu_2024, title={Molecular dynamics simulation of steady-state droplet condensation on a fiber in direct contact membrane distillation settings (vol 368, 120736, 2022)}, volume={393}, ISSN={["1873-3166"]}, DOI={10.1016/j.molliq.2023.123525}, journal={JOURNAL OF MOLECULAR LIQUIDS}, author={Raza, Saqlain and He, Jixiong and Tafreshi, Hooman V and Liu, Jun}, year={2024}, month={Jan} }
 @article{kumar_gautam_atri_tafreshi_pourdeyhimi_2024, title={The impact of particle deposition on collection efficiency of electret fibers}, url={https://doi.org/10.1016/j.jaerosci.2024.106426}, DOI={10.1016/j.jaerosci.2024.106426}, journal={Journal of Aerosol Science}, author={Kumar, A. and Gautam, S. and Atri, S. and Tafreshi, H.V. and Pourdeyhimi, B.}, year={2024}, month={Sep} }
 @article{rahman_gautam_tafreshi_pourdeyhimi_2024, title={The role of 3D electrostatic field in modeling the electrospinning process}, volume={135}, ISSN={["1089-7550"]}, url={https://doi.org/10.1063/5.0187859}, DOI={10.1063/5.0187859}, abstractNote={Electrospinning is a cost-effective but very intricate method of producing polymeric nanofibers at room temperature. Unfortunately however, it is extremely difficult to predict the diameter or other properties of the fibers produced via electrospinning a prior. In this paper, we present a new approach to simulate fiber formation during electrospinning. Our work builds on the mathematical framework that was originally developed by Reneker and Yarin in 2000. Our approach incorporates the 3D electrostatic field that surrounds the fiber in a Lagrangian discrete particle tracking algorithm that tracks the trajectory of the fiber in air and predicts its deposition velocity and diameter. We investigate the effects of electrostatic field spatial variation on fiber electrospinning and compare our results with those obtained using a constant electrostatic field, the traditional approach, and with experiments (conducted using polyurethane). We considered three different electrospinning configurations of single-needle-plate-collector, single-needle-drum-collector, and two-needles-drum-collector to investigate how different electrostatic fields impact fiber formation. The computational model developed in this work helps to advance the current state of the art in modeling the electrospinning process.}, number={1}, journal={JOURNAL OF APPLIED PHYSICS}, author={Rahman, S. M. and Gautam, S. and Tafreshi, H. V. and Pourdeyhimi, B.}, year={2024}, month={Jan} }
 @article{bhatta_tafreshi_pourdeyhimi_2024, title={Toward formulating coalescence filtration: Characterizing wetting saturation via centrifugal force}, volume={170}, ISSN={["1879-3533"]}, url={https://doi.org/10.1016/j.ijmultiphaseflow.2023.104641}, DOI={10.1016/j.ijmultiphaseflow.2023.104641}, abstractNote={Coalescence filtration is the removal of dispersed droplets from a gas or from an immiscible liquid using a fibrous filter. Coalescing filters operate under a partially-saturated condition where some of the filter pores are filled with accumulated droplets. To date, there exists no theory that can predict the filtration efficiency of a coalescing filter and this is due to the complicated coupling between the aerodynamic field inside the filter and the capillarity of the fibers. This paper presents a new approach to study coalescence filtration by replacing the aerodynamic field inside the filter with a centrifugal force field and to thereby decouple the role of fiber properties from that of the airflow in fluid accumulation in a filter. This paper is only the first step towards developing the above mathematical theory for coalescence filtration. In the current study, we use numerical simulation and experiment to compare desaturation of a liquid-saturated fibrous media via centrifugal force (new) and via compressed air (traditional). For the simulations, we used the volume-of-fluid (VOF) method implemented in ANSYS software, and for the experiments, we used a Porometer for the pressure-driven desaturation, and a custom-made setup inside a swing-bucket centrifuge for the centrifugal desaturation. The experiments were conducted using a nonwoven fabric infused with mineral oil. Pressure-driven and centrifugal desaturation processes were compared with one another, and the advantages of the latter were discussed in detail.}, journal={INTERNATIONAL JOURNAL OF MULTIPHASE FLOW}, author={Bhatta, Nishant and Tafreshi, Hooman V. and Pourdeyhimi, Behnam}, year={2024}, month={Jan} }
 @article{kumar_gautam_atri_tafreshi_pourdeyhimi_2023, title={Importance of Dipole Orientation in Electrostatic Aerosol Filtration}, volume={39}, ISSN={["1520-5827"]}, url={https://doi.org/10.1021/acs.langmuir.3c02016}, DOI={10.1021/acs.langmuir.3c02016}, abstractNote={Electrostatic charge is a major part of modern-day aerosol filtration media (e.g., N95 respirators and surgical facemasks) that has remained poorly understood due to its complicated physics. As such, charging a fibrous material has relied on empiricism in dire need of a mathematical foundation to further advance product design and optimization. In this concern, we have conducted a series of numerical simulations to improve our understanding of how an electrostatically charged fiber captures airborne particles and to quantify how the fiber's dipole orientation impacts its capture efficiency. Special attention was paid to the role of Coulomb and dielectrophoretic forces in the capture of particles of different charge polarities (e.g., particles having a Boltzmann charge distribution). Simulation results were compared with the predictions of the popular empirical correlations from the literature and discussed in detail. Predictions of the empirical correlations better agreed with the simulation results obtained for fibers with a dipole perpendicular to the flow direction rather than for fibers with a dipole parallel to the flow. This indicates that such empirical correlations are more suitable for filters charged via contact electrification (friction charging), where the dipoles are mostly perpendicular to the flow direction, and less suitable for corona-charged media, where the fiber dipoles are generally parallel to the flow direction.}, number={49}, journal={LANGMUIR}, author={Kumar, A. and Gautam, S. and Atri, S. and Tafreshi, H. V. and Pourdeyhimi, B.}, year={2023}, month={Nov}, pages={17653–17663} }
 @article{jamali_atri_gautam_saleh_tafreshi_pourdeyhimi_2023, title={Macroscale modeling of electrostatically charged facemasks}, volume={4}, ISSN={["1521-7388"]}, url={https://publons.com/wos-op/publon/65200080/}, DOI={10.1080/02786826.2023.2203188}, abstractNote={Abstract In this study, the instantaneous collection efficiency and pressure drop of an N95 facemask is numerically simulated in a setting similar (but not identical) to that used by NIOSH to certify N95 respirators. More specifically, a CPU-friendly macroscale model is developed, for the first time, to simulate the performance of an electrostatically-charged facemask when the mask is clean and when it is loaded with neutral or neutralized nanoparticles. The simulations were performed using ANSYS software enhanced with in-house subroutines, and they were calibrated using the experimental data reported in the literature for the initial efficiency of N95 masks. In addition, a correction factor was developed for the Kozeny-Carman permeability equation to expand its application to the case of nanoparticle-deposits, where the dendrites porosity is very high and the aerodynamic slip is expected to occur. Copyright © 2023 American Association for Aerosol Research}, journal={AEROSOL SCIENCE AND TECHNOLOGY}, author={Jamali, M. and Atri, S. and Gautam, S. and Saleh, A. M. and Tafreshi, H. V. and Pourdeyhimi, B.}, year={2023}, month={Apr} }
 @article{gautam_saleh_tafreshi_radney_pourdeyhimi_2023, title={Macroscale simulation of particle loading in electrostatically charged filters}, volume={173}, ISSN={["1879-1964"]}, url={https://doi.org/10.1016/j.jaerosci.2023.106212}, DOI={10.1016/j.jaerosci.2023.106212}, abstractNote={Existing studies have shown that particle collection efficiency of a charged filter tends to decrease with particle loading to a certain extent, then increase with further loading. This contrasts with pressure drop which monotonically increases with particle loading. This trend in particle collection efficiency is due to a variety of factors including, but not limited to, neutralization and aerodynamic shielding of the fibers' electrostatic field. The current paper presents a semi-empirical macroscale simulation method to predict the instantaneous pressure drop and particle collection efficiency of an electrostatically charged filter during the early stages of particle loading. The simulations were performed by using ANSYS software enhanced with a series of in-house subroutines. The simulation results are compared with experimental data (for calibration and validation) obtained from testing a bipolarly-charged (55 μC m−2) polypropylene filter exposed to different levels of nanoparticle loadings. The filter media was loaded (both experimentally and computationally) with polydisperse NaCl nanoparticles (count median diameter of 75 nm) having charge values of ±1e. The loaded media were then tested (experimentally and computationally) with NaCl nanoparticles spanning 10 nm–500 nm in electrical mobility diameter (from TSI 3160 filter tester) having a Fuchs charge distribution. In addition, a high-porosity conditional factor was developed for the Kozeny-Carman permeability equation to expand its application to the case of nanoparticle deposits, where the dendrites' porosity is very high, and aerodynamic slip is expected to occur.}, journal={JOURNAL OF AEROSOL SCIENCE}, author={Gautam, S. and Saleh, A. M. and Tafreshi, H. V. and Radney, J. G. and Pourdeyhimi, B.}, year={2023}, month={Sep} }
 @article{liu_chaparro_tian_jia_gosser_gaumer_ross_tafreshi_lannutti_2023, title={Visualization of porosity and pore size gradients in electrospun scaffolds using laser metrology}, volume={18}, ISSN={["1932-6203"]}, url={https://doi.org/10.1371/journal.pone.0282903}, DOI={10.1371/journal.pone.0282903}, abstractNote={We applied a recently developed method, laser metrology, to characterize the influence of collector rotation on porosity gradients of electrospun polycaprolactone (PCL) widely investigated for use in tissue engineering. The prior- and post-sintering dimensions of PCL scaffolds were compared to derive quantitative, spatially-resolved porosity ‘maps’ from net shrinkage. Deposited on a rotating mandrel (200 RPM), the central region of deposition reaches the highest porosity, ~92%, surrounded by approximately symmetrical decreases to ~89% at the edges. At 1100 RPM, a uniform porosity of ~88–89% is observed. At 2000 RPM, the lowest porosity, ~87%, is found in the middle of the deposition, rebounding to ~89% at the edges. Using a statistical model of random fiber network, we demonstrated that these relatively small changes in porosity values produce disproportionately large variations in pore size. The model predicts an exponential dependence of pore size on porosity when the scaffold is highly porous (e.g., >80%) and, accordingly, the observed porosity variation is associated with dramatic changes in pore size and ability to accommodate cell infiltration. Within the thickest regions most likely to ‘bottleneck’ cell infiltration, pore size decreases from ~37 to 23 μm (38%) when rotational speeds increased from 200 to 2000 RPM. This trend is corroborated by electron microscopy. While faster rotational speeds ultimately overcome axial alignment induced by cylindrical electric fields associated with the collector geometry, it does so at the cost of eliminating larger pores favoring cell infiltration. This puts the bio-mechanical advantages associated with collector rotation-induced alignment at odds with biological goals. A more significant decrease in pore size from ~54 to ~19 μm (65%), well below the minimum associated with cellular infiltration, is observed from enhanced collector biases. Finally, similar predictions show that sacrificial fiber approaches are inefficient in achieving cell-permissive pore sizes.}, number={3}, journal={PLOS ONE}, author={Liu, Yi-xiao and Chaparro, Francisco J. and Tian, Ziting and Jia, Yizhen and Gosser, John and Gaumer, Jeremy and Ross, Liam and Tafreshi, Hooman and Lannutti, John J.}, editor={Yong, XinEditor}, year={2023}, month={Mar} }
 @inproceedings{moghadam_tafreshi_2022, title={Adhesion Forces on A Droplet Sandwiched between Hydrophobic Fibrous Layers}, booktitle={13th World Filtration Congress}, author={Moghadam, A. and Tafreshi, H.V.}, year={2022}, month={Oct} }
 @inproceedings{farhan_tafreshi_2022, title={Detaching Water Droplets from a Fiber using a Magnetic Field}, booktitle={13th World Filtration Congress}, author={Farhan, M. and Tafreshi, H.V.}, year={2022}, month={Oct} }
 @article{raza_he_tafreshi_liu_2022, title={Molecular dynamics simulation of steady-state droplet condensation on a fiber in direct contact membrane distillation settings}, volume={368}, ISSN={["1873-3166"]}, url={https://publons.com/wos-op/publon/58788381/}, DOI={10.1016/j.molliq.2022.120736}, abstractNote={• Dynamics of droplet condensation-evaporation was simulated in Direct Contact Membrane Distillation (DCMD) environment. • A novel methodology for achieving steady-state supply of water during an infinitely long period was developed. • The fiber was modelled as a tri-layer structure for appropriate depiction of the actual process. • Droplet formation on fibers can be prevented if the fiber’s Young-Laplace contact angle is greater than a critical value. • Our work provides design guidelines for DCMD membranes based on geometric and operational parameters. Understanding the dynamics of droplet condensation–evaporation behavior on fibers is important for improving the performance of fibrous membranes that are used in water purification applications, e.g., Direct Contact Membrane Distillation (DCMD). DCMD is a promising method of purifying water when low-grade waste heat or renewable energies are available. However, DCMD suffers from low throughput mass flux, and it is also prone to membrane flooding. We used molecular dynamics simulations in this work as the conventional (experimental or computational) methods do not have the required atomistic resolution to reveal the dynamics of water condensation–evaporation on the surface of fibers. Our simulations indicate that vapor flux across the membrane remains constant (with no droplet formation on the fiber) when the fibers’ Young–Laplace Contact Angle (YLCA) is greater than a critical value at which condensation is suppressed. However, mass flux decreases with time at lower YLCAs due to the formation and growth of water droplets on the fibers, which could ultimately lead to membrane flooding. We also studied the impact of feed temperature, permeate temperature, fiber diameter, fiber position, and domain size on the fiber critical YLCA. Optimizing these parameters allows the use of a wide array of materials in membrane fabrication, including even hydrophilic materials, while preventing membrane flooding and also enhancing mass flux. In this work, we also present a novel methodology to simulate steady-state droplet condensation–evaporation process in the framework of molecular dynamics simulation, i.e., simulation times >∼10 ns, in contrast to the quasi-steady-state simulations (simulation time <∼2 ns) reported in most previous studies. Our work demonstrates a simulation platform to study the dynamics of the water condensation–evaporation on fibers and can be used to guide the design of DCMD membranes.}, journal={JOURNAL OF MOLECULAR LIQUIDS}, publisher={Elsevier BV}, author={Raza, Saqlain and He, Jixiong and Tafreshi, Hooman V. and Liu, Jun}, year={2022}, month={Dec} }
 @article{rahman_tafreshi_pourdeyhimi_2022, title={Physics-based deep neural network model to guide electrospinning polyurethane fibers}, volume={9}, ISSN={["1097-4628"]}, url={https://doi.org/10.1002/app.53108}, DOI={10.1002/app.53108}, abstractNote={Abstract}, journal={JOURNAL OF APPLIED POLYMER SCIENCE}, author={Rahman, S. Mashfiqur and Tafreshi, Hooman Vahedi and Pourdeyhimi, Behnam}, year={2022}, month={Sep} }
 @inproceedings{tafreshi_2022, title={Studying Filtration through Micro- And Macro-Scale Modeling and Experiment}, booktitle={13th World Filtration Congress}, author={Tafreshi, H.V.}, year={2022}, month={Oct} }
 @article{holweger_jamali_tafreshi_2021, title={Centrifugal Detachment of Compound Droplets from Fibers}, volume={37}, ISSN={["0743-7463"]}, url={https://doi.org/10.1021/acs.langmuir.0c03317}, DOI={10.1021/acs.langmuir.0c03317}, abstractNote={This article presents the first experimental-computational study on the centrifugal detachment of a compound droplet (e.g., a primary water droplet cloaked by an immiscible oil) from a fiber. The work was intended to establish a method for quantifying the force needed to detach compound droplets of different compositions from a fiber. More importantly, our study was aimed at improving the understanding of the interplay between interfacial and external forces acting on a compound droplet during forceful detachment. The experiments were conducted using DI water, for the primary droplet, and silicone or mineral oil, for the cloaking fluid. It was observed from the experiments that the silicone-oil-cloaked droplets behave differently from the mineral-oil-cloaked droplets. It was also observed that detachment force decreases with increasing the oil-to-water volume ratio. The simulations were performed using the Surface Evolver (SE) finite element code programmed for the complicated four-phase (air, water, oil, and solid) interfacial problem at hand. Our simulations revealed the evolution of the interfacial forces between the interacting phases under an increasing external body force on the droplet. The simulations also allowed us to define effective interfacial tensions and contact angles for detaching compound droplets, for the first time. Reasonable agreement was observed between the experimental measurements and computational results.}, number={2}, journal={LANGMUIR}, publisher={American Chemical Society (ACS)}, author={Holweger, H. J. and Jamali, M. and Tafreshi, H. Vahedi}, year={2021}, month={Jan}, pages={928–938} }
 @article{jamali_mehta_holweger_amrei_tafreshi_2021, title={Controlling detachment residue via magnetic repulsion force}, volume={118}, ISSN={["1077-3118"]}, url={https://doi.org/10.1063/5.0052141}, DOI={10.1063/5.0052141}, abstractNote={This work demonstrates the possibility of using a magnetic repulsion force to reduce the volume of the residue that remains on a surface after detachment of a ferrofluid droplet. This technique provides a means for controlling the detachment residue by controlling the spatial strength of the magnetic field used for droplet detachment. The experimental technique developed in this work can help us to improve our understanding of the underlying physics of droplet adhesion to a surface and the mechanics of residue formation during droplet detachment.}, number={19}, journal={APPLIED PHYSICS LETTERS}, author={Jamali, M. and Mehta, K. S. and Holweger, H. and Amrei, M. M. and Tafreshi, H.}, year={2021}, month={May} }
 @inproceedings{tafreshi_2021, title={Fluid Mechanics of Droplet Fiber Adhesion}, booktitle={FiltCon 2021, American Filtration and Separations Society}, author={Tafreshi, H.V.}, year={2021}, month={Apr} }
 @inproceedings{farhan_tafreshi_2021, title={Novel Method to Measure Droplet Contact Angle with a Fiber}, booktitle={13th World Filtration Congress}, author={Farhan, N.M. and Tafreshi, H.V.}, year={2021}, month={Oct} }
 @article{jamali_tafreshi_2021, title={Numerical simulation of two-phase droplets on a curved surface using Surface Evolver}, volume={629}, ISSN={["1873-4359"]}, url={https://publons.com/wos-op/publon/48546038/}, DOI={10.1016/j.colsurfa.2021.127418}, abstractNote={In this paper, we present a new approach for using the Surface Evolver (SE) finite element program to simulate the 3-D shape of a droplet on a curved surface. The approach proposed in this paper circumvents the need for carrying out complicated derivations to obtain analytical expressions for the total energy of the interfacial areas between air, liquid, and solid surfaces. More specifically, we use the solid–liquid surface energy in place of the contact angle when simulating a droplet using SE. This approach also makes it easier to use SE to model a two-phase droplet (e.g., a compound droplet) on a solid surface. To better illustrate our approach, the 3-D shape of single-phase and compound pendant droplets are simulated on a hydrophobic spherical surface in the presence of gravitational and magnetic fields. For validation purposes, our computational results are compared to dedicated experimental data obtained by compounding water droplets with oil-based ferrofluids of different surface tensions.}, journal={COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS}, author={Jamali, M. and Tafreshi, H. Vahedi}, year={2021}, month={Nov} }
 @article{pourdeyhimi_schick_groten_tafreshi_2021, title={Respiratory Effectiveness of Cloth Masks}, volume={2}, ISSN={2690-2656 2690-2656}, url={http://dx.doi.org/10.37714/josam.v2i4.60}, DOI={10.37714/josam.v2i4.60}, abstractNote={The shortage of medical masks and respirators led to an explosion of cloth mask offerings.  In the absence of any regulatory requirements, and appropriate guidance, the medical masks vary greatly in their performance and have become more of a fashion item. 
 
We review the filtration mechanisms and test methods and show data on common offerings.  Almost exclusively, the data suggest that cloth masks do not offer much of a protection, and many are poorly designed with only the pressure drop and fogging in mind; these compromise the performance of the entire mask. While cloth masks do not offer significant respiratory protection, it is still critical that masks are worn during pandemics regardless in that they do reduce the number of aerosols expelled by the wearer.}, number={4}, journal={The Journal of Science and Medicine}, publisher={Cortical Metrics LLC.}, author={Pourdeyhimi, Behnam and Schick, Simon and Groten, Robert and Tafreshi, Hooman Vahedi}, year={2021}, month={Feb} }
 @misc{jamali_tafreshi_2021, title={Studying droplet adhesion to fibers using the magnetic field: a review paper}, volume={62}, ISSN={["1432-1114"]}, url={https://doi.org/10.1007/s00348-021-03258-9}, DOI={10.1007/s00348-021-03258-9}, number={8}, journal={EXPERIMENTS IN FLUIDS}, publisher={Springer Science and Business Media LLC}, author={Jamali, Mohammad and Tafreshi, Hooman V}, year={2021}, month={Aug} }
 @article{esteves_gornick_alqurwani_koenig-lovejoy_abdelrazeq_khraisheh_forzano_gad-el-hak_tafreshi_mcleskey_2020, title={Activated carbon-doped polystyrene fibers for direct contact membrane desalination}, volume={3}, ISSN={2522-5731 2522-574X}, url={http://dx.doi.org/10.1007/s42247-020-00107-z}, DOI={10.1007/s42247-020-00107-z}, number={6}, journal={Emergent Materials}, publisher={Springer Science and Business Media LLC}, author={Esteves, Richard J. Alan and Gornick, Veronica and Alqurwani, Dea Santi and Koenig-Lovejoy, Joshua and Abdelrazeq, Haneen and Khraisheh, Majeda and Forzano, Anna V. and Gad-el-Hak, Mohamed and Tafreshi, Hooman Vahedi and McLeskey, James T., Jr}, year={2020}, month={May}, pages={807–814} }
 @article{jamali_tafreshi_2020, title={Measuring Force of Droplet Detachment from Hydrophobic Surfaces via Partial Cloaking with Ferrofluids}, volume={36}, url={https://doi.org/10.1021/acs.langmuir.0c00532}, DOI={10.1021/acs.langmuir.0c00532}, abstractNote={This paper presents a new approach to measure the force required to detach a water (a polar liquid) droplet from a hydrophobic surface. This is done by partially cloaking the droplet with a high-surface tension oil-based ferrofluid and using a magnet to apply a controllable body force to the resulting compound droplet. Placing the assembly on a sensitive scale, the magnet can then be brought closer to the droplet to detach it from the surface while recording the forces applied to the droplet. The work presented here is novel as it uses the concept of partial cloaking in which the solid-droplet contact area is not contaminated by the ferrofluid (and the measured forces do not need postprocessing). Our study is accompanied by numerical simulations aimed at improving our understanding of the interplay between the interfacial forces in a two-phase droplet under the influence of a strong (detaching) body force, as well as at providing additional data for in-depth analyses of these forces. In particular, minimum ferrofluid volume required for successful water droplet detachment from hydrophobic surfaces is computed for ferrofluids of different surface tensions, and they are compared to experimental data obtained from detaching water droplets from electrospun polystyrene coatings. It is also shown that the detachment force measured via partial cloaking is independent of the volume of the ferrofluid used for the experiment.}, number={22}, journal={Langmuir}, publisher={American Chemical Society (ACS)}, author={Jamali, Mohammad and Tafreshi, Hooman Vahedi}, year={2020}, month={Jun}, pages={6116–6125} }
 @article{yousefi_tafreshi_2020, title={Modeling electrospun fibrous structures with embedded spacer particles: Application to aerosol filtration}, volume={235}, ISSN={1383-5866}, url={http://dx.doi.org/10.1016/j.seppur.2019.116184}, DOI={10.1016/j.seppur.2019.116184}, abstractNote={This work presents a physics-based modeling technique to simulate the 3-D microstructure of electrospun fibrous media with embedded spacer particles. The model accepts inputs like diameter, basis weight, deposition velocity, and bending properties for the fibers as well as diameter and basis weight for the spacer particles. The model then predicts morphological parameters like filter porosity and filter thickness, among many others. The work presented in this paper is the first to report the effects of spacer particles with different diameters or basis weights on the thickness and solid volume fraction of spacer-embedded fibrous media. Such morphological information is then used for collection efficiency and pressure drop predictions when challenged with aerosol particles in the particle diameter range of 20 nm to 5 µm at a face velocity of 10 cm/s. Our results indicate that adding spacer particles to a fibrous filter can lower its collection efficiency and pressure drop, but the reduction in the pressure drop will be at a higher rate resulting in better filters, i.e., filters with better quality factors.}, journal={Separation and Purification Technology}, publisher={Elsevier BV}, author={Yousefi, S.H. and Tafreshi, H.V.}, year={2020}, month={Mar}, pages={116184} }
 @article{yousefi_tafreshi_2020, title={Novel approach to model microstructure of dust-deposits comprised of polydisperse particles of arbitrary shapes}, volume={244}, ISSN={1383-5866}, url={http://dx.doi.org/10.1016/j.seppur.2020.116844}, DOI={10.1016/j.seppur.2020.116844}, abstractNote={Morphology of airborne particles plays a key role in the growth rate of dust-cake formed on an exposed solid surface, or on the face of an air filter. The work presented in this paper reports on a fast and flexible algorithm to simulate the microstructure of dust-cakes resulting from deposition of non-inertial airborne particles of arbitrary shapes. Our approach is based on representing a non-spherical particle as an assembly of spherical beads connected to one another via springs and dampers. This mass-spring-damper (MSD) model allows one to study the effects of particle shape, particle size, and particle rigidity on the thickness and porosity of the dust-cakes that result from deposition of such aerosol particles in different applications. In aerosol filtration applications for instance, the ability to predict the thickness and porosity of a dust-cake comprised of non-spherical particles is needed before one can predict the pressure drop or collection efficiency of a dust-loaded filter. For demonstration purposes in this paper, dust-cakes comprised of particles with cubical and spherocylindrical shapes as well as Jacks-toy and Plus-sign shapes are simulated and discussed.}, journal={Separation and Purification Technology}, publisher={Elsevier BV}, author={Yousefi, S.H. and Tafreshi, H.V.}, year={2020}, month={Aug}, pages={116844} }
 @article{moghadam_tafreshi_2020, title={On liquid bridge adhesion to fibrous surfaces under normal and shear forces}, volume={589}, ISSN={0927-7757}, url={http://dx.doi.org/10.1016/j.colsurfa.2020.124473}, DOI={10.1016/j.colsurfa.2020.124473}, abstractNote={This paper reports on adhesion forces between a liquid bridge and two parallel plates coated with electrospun fibers experimentally and computationally. For the experiments, a DI water droplet containing 15% glycerol was placed on one of the plates and compressed, stretched, or sheared using the other plate. The assembly was mounted on a sensitive scale to measure the forces applied to the plates during the experiment. For the computational part, an efficient modeling approach was developed to predict the 3-D shape of the liquid bridge and to calculate its resistance to normal and tangential forces in the presence of contact angle hysteresis effects, using the Surface Evolver finite element code. Despite the inherent non-uniformity of the fibrous surfaces used in the experiments and the simplifying assumptions considered for the simulations, reasonable agreement was observed between the measurements and their computational counterparts. In addition, the hysteresis behavior of a liquid bridge during a compression–stretching process is mapped in an energy or force diagram versus spacing between the plates using radius-constant and contact-angle-constant lines describing the triple contact-line. It was also observed that a liquid bridge between two electrospun coatings tends to maintain its symmetricity despite the anisotropic roughness of the coatings, due perhaps to the minuteness of the electrospun fibers relative to the size of the liquid bridge.}, journal={Colloids and Surfaces A: Physicochemical and Engineering Aspects}, publisher={Elsevier BV}, author={Moghadam, A. and Tafreshi, H.V.}, year={2020}, month={Feb}, pages={124473} }
 @article{abdelrazeq_khraisheh_al momani_mcleskey_hassan_gad-el-hak_tafreshi_2020, title={Performance of electrospun polystyrene membranes in synthetic produced industrial water using direct-contact membrane distillation}, volume={493}, ISSN={0011-9164}, url={http://dx.doi.org/10.1016/j.desal.2020.114663}, DOI={10.1016/j.desal.2020.114663}, abstractNote={Desalination of produced water in the gulf petrochemical industry is a continuing challenge to major research groups in the field. With a focus on produced water from desalination plants, it has become crucial to define and follow specific protocol in wastewater purification technologies. In this work, an optimized guideline for direct contact membrane distillation (DCMD) was developed and implemented. A bench-scale DCMD unit was performed under optimum process parameters of feed and distillation inlet temperatures of TFeed = 60 °C and TDist = 20 °C, respectively. A low flow rate of 0.03 L/min was used to avoid wetting of the fabricated membrane. A hydrophobic polystyrene flat sheet was prepared in the labs using a custom-made electrospinning apparatus. The effect of varying concentrations on the hydrophobic polystyrene membrane was studied using a high concentration brine feed (C1 ≈ 75,500 ppm) and another feed of lower concentration (C2 ≈ 25,200 ppm). A high salt rejection rate of 99% was achieved. The morphological structure, pore size and fiber length was analyzed using SEM. Conductivity measurements have confirmed an improved permeate quality of 99%. Thus, as per the DCMD performance of the polystyrene membrane, the generated permeate indicates that the membrane performance may have scalable potential contribution to industrial wastewater purification.}, journal={Desalination}, publisher={Elsevier BV}, author={Abdelrazeq, Haneen and Khraisheh, Majeda and Al Momani, Fares and McLeskey, James T., Jr and Hassan, Mohammad K. and Gad-el-Hak, Mohamed and Tafreshi, Hooman Vahedi}, year={2020}, month={Nov}, pages={114663} }
 @inproceedings{tafreshi_2020, title={Understanding Airborne Dust and Droplet Filtration via Multiscale Modeling and Experiment}, booktitle={FiltXpo 2020}, author={Tafreshi, H.V.}, year={2020}, month={Feb} }
 @inproceedings{moghadam_tafreshi_pourdeyhimi_2019, title={Characterizing Nonwoven Fibrous Materials via Realistic Microstructural Simulation}, booktitle={American Filtration and Separations Society}, author={Moghadam, A. and Tafreshi, H.V. and Pourdeyhimi, B.}, year={2019}, month={Apr} }
 @article{moghadam_yousefi_tafreshi_pourdeyhimi_2019, title={Characterizing nonwoven materials via realistic microstructural modeling}, volume={211}, ISSN={1383-5866}, url={http://dx.doi.org/10.1016/j.seppur.2018.10.018}, DOI={10.1016/j.seppur.2018.10.018}, abstractNote={A physics-based nonwoven structure generation model is presented in this work. The model is capable of incorporating the mechanical properties of the fibers in the simulations by treating each fiber as an array of beads connected to one another via springs and dampers. Our algorithm can realistically simulate the bending of the fibers at fiber–fiber crossovers or when external forces are applied to the fibers during fiber deposition process. In fact, a unique attribute of the modeling approach presented in this work is that it can be modified to emulate, to some extent, the manufacturing process by which the nonwoven media have been produced. Unlike most previous structure generation models, our mass-spring-damper algorithm does not require the thickness or porosity of the media to be fed to the model as an input, and it is also capable of avoiding fiber–fiber overlaps. For demonstration purposes, virtual media with bimodal fiber diameter or contact angle distributions were produced and used to estimate the pressure required for water to penetrate through a hydrophobic fibrous membrane, i.e., the so-called liquid entry pressure (LEP). The LEP calculations here are based on a simplifying assumption that the air–water interface remains intact across the width of the simulation domain as it travels throughout the media. Effects of fiber diameter(s), fiber orientations, or fiber contact angle(s) on LEP are simulated and discussed in detail.}, journal={Separation and Purification Technology}, publisher={Elsevier BV}, author={Moghadam, A. and Yousefi, S.H. and Tafreshi, H. Vahedi and Pourdeyhimi, B.}, year={2019}, month={Mar}, pages={602–609} }
 @article{aziz_tafreshi_2019, title={Competing forces on a liquid bridge between parallel and orthogonal dissimilar fibers}, volume={15}, url={https://doi.org/10.1039/C9SM00489K}, DOI={10.1039/C9SM00489K}, abstractNote={This paper presents a detailed investigation on the mechanical forces acting on a liquid bridge between dissimilar fibers in parallel and orthogonal configurations.}, number={35}, journal={Soft Matter}, publisher={Royal Society of Chemistry (RSC)}, author={Aziz, Hossain and Tafreshi, Hooman V.}, year={2019}, pages={6967–6977} }
 @article{jamali_tafreshi_pourdeyhimi_2019, title={Easy-to-use correlations to estimate droplet mobility on hydrophobic fibrous coatings}, volume={582}, ISSN={["1873-4359"]}, url={https://publons.com/wos-op/publon/40951443/}, DOI={10.1016/j.colsurfa.2019.123867}, abstractNote={While a water droplet beads up on a hydrophobic fibrous surface, it does not necessarily detach or move on the surface under its own weight. The underlying physics of droplet adhesion to a rough surface is very complicated, and the ability to engineer a fibrous texture that promotes or prevents droplet mobility for droplets of different liquids has been a long-standing challenge. In this concern, the current work is devised to develop easy-to-use correlations for the force needed to detach a droplet from a hydrophobic fibrous coating in the in-plane and out-of-plane directions. These correlations are obtained by first writing an equation for the balance of forces acting on a detaching droplet in terms of its geometrical dimensions at the moment of detachment, and then relating these dimensions to those in the absence of an external force via curve fitting to a series of computational data. These easy-to-use correlations only require the physical properties of the fibrous coatings (e.g., fiber diameter, fiber spacing, and fiber contact angle) and the droplets (e.g., volume and surface tension) as inputs, and they can therefore be used to optimize the surface geometry prior to manufacturing. To examine their accuracy, predictions of these correlations are compared to experimental data obtained for droplet detachment from fibrous mats with fibers having a diameter of about two orders of magnitude smaller than those considered in developing the correlations.}, journal={COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS}, author={Jamali, M. and Tafreshi, H. Vahedi and Pourdeyhimi, B.}, year={2019}, month={Dec} }
 @inproceedings{yousefi_tafreshi_pourdeyhimi_2019, title={Effects of Electrospinning Parameters on Microstructure of Polystyrene Fibrous Mats}, booktitle={American Filtration and Separations Society}, author={Yousefi, S.H. and Tafreshi, H.V. and Pourdeyhimi, B.}, year={2019}, month={Apr} }
 @article{yousefi_tang_tafreshi_pourdeyhimi_2019, title={Empirical model to simulate morphology of electrospun polycaprolactone mats}, volume={136}, ISSN={0021-8995 1097-4628}, url={http://dx.doi.org/10.1002/APP.48242}, DOI={10.1002/app.48242}, abstractNote={ABSTRACT}, number={46}, journal={Journal of Applied Polymer Science}, publisher={Wiley}, author={Yousefi, S. H. and Tang, C. and Tafreshi, H. Vahedi and Pourdeyhimi, B.}, year={2019}, month={Jul}, pages={48242} }
 @inproceedings{tafreshi_2019, title={Fluid and Particle Transport through Fibrous Media and Fibrous Coatings}, booktitle={American Filtration and Separations Society}, author={Tafreshi, H.V.}, year={2019}, month={Apr} }
 @inproceedings{farhan_aziz_ojaghlou_holweger_tafreshi_2019, title={On the Adhesion Force between a Droplet and a Single Fiber}, booktitle={American Filtration and Separations Society}, author={Farhan, N.M. and Aziz, H. and Ojaghlou, N. and Holweger, H. and Tafreshi, H.V.}, year={2019}, month={Apr} }
 @article{jamali_tafreshi_pourdeyhimi_2019, title={Penetration of liquid droplets into hydrophobic fibrous materials under enhanced gravity}, volume={125}, ISSN={0021-8979 1089-7550}, url={http://dx.doi.org/10.1063/1.5092227}, DOI={10.1063/1.5092227}, abstractNote={In this paper, experimental and numerical simulations were devised to study and formulate the force required for forcing a droplet to penetrate into a thin nonwetting fibrous structure. Due to the complexity of the problem at hand, we considered only thin fibrous structures comprised of parallel or orthogonally layered fibers. The experiments were conducted using ferrofluid droplets placed on electrospun polystyrene fibrous coatings. A permanent magnet was used to apply a body force to the droplets from below, and the assembly was placed on a sensitive scale for measuring the applied force. Numerical simulations were conducted using the Surface Evolver finite element code validated through comparison with dedicated experimental results. We studied how the force needed to initiate droplet spontaneous penetration into a thin fibrous coating varies with varying the volume of the droplet or the geometric properties of the coating. Using a combination of simulation results and experimental observations, easy-to-use but approximate expressions were derived and used to predict the force required to initiate droplet spontaneous penetration into the above-mentioned fibrous material. These analytical expressions allow one to circumvent the need for running a numerical simulation for each and every droplet–coating combination of interest and thereby expand the application of our work to conditions different from those considered here.}, number={14}, journal={Journal of Applied Physics}, publisher={AIP Publishing}, author={Jamali, M. and Tafreshi, H.V. and Pourdeyhimi, B.}, year={2019}, month={Apr}, pages={145304} }
 @article{farhan_aziz_tafreshi_2019, title={Simple method for measuring intrinsic contact angle of a fiber with liquids}, volume={60}, url={https://doi.org/10.1007/s00348-019-2733-2}, DOI={10.1007/s00348-019-2733-2}, number={5}, journal={Experiments in Fluids}, publisher={Springer Science and Business Media LLC}, author={Farhan, Noor M. and Aziz, H. and Tafreshi, H. Vahedi}, year={2019}, month={May} }
 @inproceedings{jamali_tafreshi_pourdeyhimi_2019, title={Understanding Droplet Mobility and Penetration in Nonwovens via Numerical Simulation and Complementary Experiment}, booktitle={American Filtration and Separations Society}, author={Jamali, M. and Tafreshi, H.V. and Pourdeyhimi, B.}, year={2019}, month={Apr} }
 @article{farhan_tafreshi_2019, title={Using Magnetic Field to Measure Detachment Force between a Nonmagnetic Droplet and Fibers}, volume={6}, url={https://doi.org/10.1021/acs.langmuir.9b01313}, DOI={10.1021/acs.langmuir.9b01313}, abstractNote={The ability to predict and/or measure the force needed to detach a droplet from a fiber (or an assembly of fibers) is important in designing efficient droplet-air or droplet-fluid separation media for a variety of applications. This paper reports on the use of magnetic force to measure the force of detachment for nonmagnetic droplets for the first time. This is accomplished by adding a small amount of ferrofluid (the secondary fluid) to the original nonmagnetic droplet (the primary fluid) to create a compound droplet with the ferrofluid nesting inside or cloaking the nonmagnetic droplet. Either way, the secondary ferrofluid can be used to induce a body force to the resulting compound droplet and thereby detach it from the fiber(s). The recorded detachment force can be used directly (the case of nesting ferrofluid) or after scaling (the case of cloaking ferrofluid) to obtain the force of detachment for the original nonmagnetic droplet. The novelty of the proposed method lies in the fact that it circumvents the need for using an external object, an airflow, or a centrifugal device for force measurement. The accuracy of our measurements was examined through comparison with validated numerical simulations as well as experimental data in the literature and good agreement was observed.}, journal={Langmuir}, publisher={American Chemical Society (ACS)}, author={Farhan, N. M. and Tafreshi, H. Vahedi}, year={2019}, month={Jun} }
 @article{tafreshi_2019, title={Virtual Modeling in Design and Testing}, journal={Filtration+Separation}, author={Tafreshi, H.V.}, year={2019}, month={Jul} }
 @article{moghadam_jamali_venkateshan_tafreshi_pourdeyhimi_2018, title={A new approach to modeling liquid intrusion in hydrophobic fibrous membranes with heterogeneous wettabilities}, volume={558}, ISSN={0927-7757}, url={http://dx.doi.org/10.1016/j.colsurfa.2018.08.051}, DOI={10.1016/j.colsurfa.2018.08.051}, abstractNote={The current paper presents an energy minimization method, implemented in the Surface Evolver code, for tracking the air–water interface intrusion in a hydrophobic fibrous membrane and thereby studying the effects of the membrane’s microstructure on its resistance to water intrusion (i.e., membrane’s liquid entry pressure). The simulation method developed in this work is computationally affordable and it is accurate in its predictions of the air–water interface shape and position inside the membrane as a function of pressure (and the size or contact angles of the fibers). Due to challenges in applying the present interface tracking method to membranes having highly complex internal microstructures (e.g., media comprised of dissimilar fibers with random three-dimensional orientations), this study is limited to membranes comprised of orthogonally oriented fibers. Application of the proposed simulation method in studying effects of fiber diameter or contact angle heterogeneity on water intrusion pressure is demonstrated for such orthogonal fibrous structures.}, journal={Colloids and Surfaces A: Physicochemical and Engineering Aspects}, publisher={Elsevier BV}, author={Moghadam, A. and Jamali, M. and Venkateshan, D.G. and Tafreshi, H.V. and Pourdeyhimi, B.}, year={2018}, month={Dec}, pages={154–163} }
 @article{jamali_tafreshi_pourdeyhimi_2018, title={Droplet Mobility on Hydrophobic Fibrous Coatings Comprising Orthogonal Fibers}, volume={34}, ISSN={["0743-7463"]}, url={https://doi.org/10.1021/acs.langmuir.8b02810}, DOI={10.1021/acs.langmuir.8b02810}, abstractNote={Water droplet mobility on a hydrophobic surface cannot be guaranteed even when the droplet exhibits a high contact angle (CA) with the surface. In fact, droplet mobility on a surface, especially a fibrous surface, has remained an unsolved empirical problem. This paper is a combined experimental-computational study focused on droplet mobility on a fibrous surface. Electrospun polystyrene (PS) coatings were used in this work for their ability to exhibit high CAs simultaneously with low droplet mobility. To simplify this otherwise complicated problem and better isolate droplet-fiber interactions, the orientation of the fibers in the coatings was limited to the x and y directions. As the earth gravity was not strong enough to mobilize small droplets on PS coatings, experiments were conducted using ferrofluid droplets, and a magnet was used to make them move on the surface. Experimentally validated numerical simulations were used to enhance our understanding of the forces acting on a droplet before moving on the surface. Effects of Young-Laplace CA and fiber-fiber spacing on droplet mobility were investigated. In particular, it was found that droplet mobility depends strongly on the balance of forces exerted on the droplet by the fibers on the receding and advancing sides.}, number={41}, journal={LANGMUIR}, publisher={American Chemical Society (ACS)}, author={Jamali, M. and Tafreshi, H. Vahedi and Pourdeyhimi, B.}, year={2018}, month={Oct}, pages={12488–12499} }
 @article{jamali_moghadam_tafreshi_pourdeyhimi_2018, title={Droplet adhesion to hydrophobic fibrous surfaces}, volume={456}, ISSN={0169-4332}, url={http://dx.doi.org/10.1016/j.apsusc.2018.06.136}, DOI={10.1016/j.apsusc.2018.06.136}, abstractNote={A water droplet can exhibit a high apparent contact angle on a hydrophobic fibrous surface. However, a high contact angle does not guarantee droplet mobility on the surface. The reasons behind droplet adhesion to a hydrophobic fibrous surface has not yet been analyzed or formulated. In this work, the force required to detach a droplet from a hydrophobic fibrous surface is investigated experimentally and computationally. Electrospun Polystyrene mats are considered for this study as they exhibit high contact angles coupled with poor droplet mobility. To better isolate the effects of microstructural properties of the mats and study their effects on droplet detachment, randomness of the fiber orientation is minimized by producing highly oriented fibers in orthogonal layers. As the earth gravity is not strong enough to detach small droplets from such surfaces, aqueous ferrofluid droplets are used in a controllable magnetic field to enhance the effect of gravity. The detachment process is recorded via a high-speed camera and the images are used to detect the moment of detachment and to analyze droplet shape before and during detachment. Numerical simulations are also conducted to provide additional insight into the physics of droplet detachment, and more importantly, to develop an equation for estimating droplet detachment force from a fibrous surface. In this paper, we discuss the effects of fiber properties, e.g., Young-Laplace contact angle or fiber spacing, on the force needed to detach a droplet from a fibrous surface.}, journal={Applied Surface Science}, publisher={Elsevier BV}, author={Jamali, M. and Moghadam, A. and Tafreshi, H. Vahedi and Pourdeyhimi, B.}, year={2018}, month={Oct}, pages={626–636} }
 @article{ojaghlou_tafreshi_bratko_luzar_2018, title={Dynamical insights into the mechanism of a droplet detachment from a fiber}, volume={14}, ISSN={1744-683X 1744-6848}, url={http://dx.doi.org/10.1039/c8sm01257a}, DOI={10.1039/c8sm01257a}, abstractNote={For all drop sizes, water residue on the fiber is maximized by using intermediate rates of forcible drop detachment.}, number={44}, journal={Soft Matter}, publisher={Royal Society of Chemistry (RSC)}, author={Ojaghlou, Neda and Tafreshi, Hooman V. and Bratko, Dusan and Luzar, Alenka}, year={2018}, pages={8924–8934} }
 @article{aziz_farhan_tafreshi_2018, title={Dynamics of Droplet Detachment from a Fiber}, volume={59}, journal={Experiment in Fluids}, author={Aziz, H. and Farhan, N. and Tafreshi, H.V.}, year={2018}, pages={122} }
 @article{yousefi_venkateshan_tang_tafreshi_pourdeyhimi_2018, title={Effects of electrospinning conditions on microstructural properties of polystyrene fibrous materials}, volume={124}, ISSN={0021-8979 1089-7550}, url={http://dx.doi.org/10.1063/1.5049128}, DOI={10.1063/1.5049128}, abstractNote={The mathematical model developed by Reneker et al. [J. Appl. Phys. 87, 4531 (2000)] and Yarin et al. [J. Appl. Phys. 89(5), 3018–3026 (2001)] for modeling filament formation in electrospinning is combined in this work with the structure generation algorithm of Venkateshan et al. [Mater. Des. 96, 27–35 (2016)] to simulate the effects of electrospinning parameters on microstructural properties (i.e., fiber diameter, thickness, and porosity) of the resulting electrospun materials. The model is calibrated using the experimental data obtained from electrospinning polystyrene (PS) fibers. The computational tool developed in this work allows one to study the effects of electrospinning parameters, such as voltage, needle-to-collector distance (NCD), or PS concentration, on the thickness and porosity of the resulting fibrous materials. For instance, it was shown that increasing the voltage or decreasing the NCD in electrospinning polystyrene results in mats with thicker fibers but smaller dimensionless thickness (or lower porosities), in agreement with experimental observations reported in the literature. In addition to serving as a characterization tool for the electrospun materials, the computational model developed in this work can be used to create accurate representations of the surface morphology or the internal geometry of fibrous materials used in a variety of applications, such as particle filtration or droplet separation.}, number={23}, journal={Journal of Applied Physics}, publisher={AIP Publishing}, author={Yousefi, S. H. and Venkateshan, D. G. and Tang, C. and Tafreshi, H. Vahedi and Pourdeyhimi, B.}, year={2018}, month={Dec}, pages={235307} }
 @article{effects of fiber wettability and size on droplet detachment residue_2018, url={https://publons.com/wos-op/publon/40959381/}, DOI={10.1007/S00348-018-2579-Z}, journal={Experiments in Fluids}, year={2018} }
 @article{ullah_khraisheh_esteves_mcleskey_alghouti_gad-el-hak_tafreshi_2018, title={Energy efficiency of direct contact membrane distillation}, volume={433}, ISSN={0011-9164}, url={http://dx.doi.org/10.1016/j.desal.2018.01.025}, DOI={10.1016/j.desal.2018.01.025}, abstractNote={Membrane distillation (MD) is a promising technology due to its ability to function using low temperature differences and low-quality heat sources, thus allowing it to operate on solar or waste heat. The flux and energy efficiency of MD are influenced by temperature and concentration polarization, process conditions, and membrane-related parameters like thickness, tortuosity, thermal conductivity, pore size, and porosity. To date, a comprehensive review of membrane and distillation parameters on energy consumption has not yet been conducted. Accordingly, this review introduces the central energy parameters for MD (e.g., energy efficiency, gained output ratio, etc.) and discusses the reported impacts of membrane properties, mass and heat transfer, feed water properties, and system parameters on the energy parameters. The application of solar energy to direct contact MD (DCMD) is also discussed. A critical analysis of the energy efficiency of DCMD processes will help to establish its strengths and limitations and provide a road map for the development of this technology for both large-scale and portable applications.}, journal={Desalination}, publisher={Elsevier BV}, author={Ullah, Ruh and Khraisheh, Majeda and Esteves, Richard J. and McLeskey, James T., Jr and AlGhouti, Mohammad and Gad-el-Hak, Mohamed and Tafreshi, H.V.}, year={2018}, month={May}, pages={56–67} }
 @article{davoudi_amrei_tafreshi_chase_2018, title={Measurement of inflection angle and correlation of shape factor of barrel-shaped droplets on horizontal fibers}, volume={204}, ISSN={1383-5866}, url={http://dx.doi.org/10.1016/j.seppur.2018.04.033}, DOI={10.1016/j.seppur.2018.04.033}, abstractNote={The properties and shapes of drops attached to fibers are important for understanding the movements of drops on fibers in applications such as coalescing filters. One of the features of the shape of a drop attached to a cylindrical fiber is an inflection in the curvature of the drop profile near the contact line between the drop and the fiber surface. Depending on the drop volume, the point of inflection may occur very close to the drop-fiber contact line, and the angle at the inflection point could mistakenly be interpreted as the intrinsic contact angle. Measurement of the angle at the inflection point improves the characterization of the drop profile for a drop-on-fiber system. Many studies provide methods that apply droplet geometric symmetry to extract the profile of drops on flat surfaces. However, none of these methods can be easily applied to drops on fibers due to the curvature of the fiber surface and its effect on the shape of the drop. In the case of drops on fibers, drop properties such as drop length, thickness, inflection angle and volume are useful to obtain the wetting properties of the fiber surfaces without knowing the liquid properties. To determine inflection angles and volumes of axisymmetric barrel-shaped droplets on fibers from 2D images of droplets profiles a polynomial fitting method for fibers (PFMF) was applied. The strategy employed detects the location of the droplet boundary, fits a polynomial to the boundary, and calculates the inflection angle and the volume of the droplet. Volume measurements using the PFMF were consistent with calculations from Surface Evolver™ program. Using the PFMF, a new correlation was generated for a shape factor characterizing the asymmetry of barrel-shaped droplets as a function of liquid properties, fiber radius, and droplet volume.}, journal={Separation and Purification Technology}, publisher={Elsevier BV}, author={Davoudi, M. and Amrei, M.M. and Tafreshi, H.V. and Chase, G.G.}, year={2018}, month={Oct}, pages={127–132} }
 @article{venkateshan_tafreshi_2018, title={Modelling droplet sliding angle on hydrophobic wire screens}, volume={538}, ISSN={0927-7757}, url={http://dx.doi.org/10.1016/j.colsurfa.2017.11.003}, DOI={10.1016/j.colsurfa.2017.11.003}, abstractNote={This work presents a detailed investigation of the droplet lower and upper contact angles on hydrophobic wire screens with different properties such as wire diameter, wire spacing, or Young–Laplace contact angle. Numerical simulation and experiment were considered to better our understanding of the factors impacting droplet sliding on a hydrophobic screen, and to quantify their importance. To conduct the numerical simulations, the screens' geometry was programed in the Surface Evolver code, and the droplet shape was obtained by minimizing the total energy of the droplet–screen system iteratively using the code's finite element solver. Good general agreement was observed between the results of our numerical simulations and experimental data. Most interestingly, it was observed that droplet sliding angle increases with increasing the wire spacing in screens with a given wire diameter. To explain this counterintuitive observation, detailed quantitative information is presented in terms of the three-phase contact line on the droplet's receding side as well as the penetration of the air–water interface into the void space between the wires. The results of our study are discussed in the context of the contemporary literature.}, journal={Colloids and Surfaces A: Physicochemical and Engineering Aspects}, publisher={Elsevier BV}, author={Venkateshan, D.G. and Tafreshi, H. Vahedi}, year={2018}, month={Feb}, pages={310–319} }
 @article{hemeda_esteves_mcleskey_gad-el-hak_khraisheh_tafreshi_2018, title={Molecular Dynamic Simulations of Fibrous Distillation Membranes}, volume={98}, ISSN={0735-1933}, url={http://dx.doi.org/10.1016/j.icheatmasstransfer.2018.09.012}, DOI={10.1016/j.icheatmasstransfer.2018.09.012}, abstractNote={The rate of heat and mass transfer through distillation membranes is typically estimated using an over-simplified, straight-cylindrical-pore approach coupled with several empirical correction factors that are included to compensate for the simplicity of the approach. In the present work, we have calculated for the first time the rate of transport of heat and mass through three-dimensional virtual membranes from first principles without the need for any empirical correction factors. More specifically, molecular dynamic (MD) simulations are conducted in idealized 3-D geometries that resemble the microstructure of a nanofiber membrane. The SPC/E molecular model and coarse-grain Pea model are considered to simulate, respectively, water molecules and air. The fibers, on the other hand, are constructed as simple metal lattice, and their contact angle with water is controlled using a scaling factor from the Lorentz–Berthelot mixing parameters. A proof-of-concept study is presented to demonstrate the capabilities of the new modeling approach in predicting the effects of the membrane's microstructural properties on the desalination performance. While the simulations are conducted at scales 3–4 orders of magnitudes smaller than an actual electrospun membrane, the conclusions can be applied membranes with more practical dimensions.}, journal={International Communications in Heat and Mass Transfer}, publisher={Elsevier BV}, author={Hemeda, A.A. and Esteves, R.J.A. and McLeskey, J.T., Jr and Gad-el-Hak, M. and Khraisheh, M. and Tafreshi, H.V.}, year={2018}, month={Nov}, pages={304–309} }
 @article{farhan_tafreshi_2018, title={Predictive Correlations for Droplet–Fiber Detachment Force}, volume={124}, journal={Journal of Applied Physics}, author={Farhan, N. and Tafreshi, H.V.}, year={2018} }
 @article{aziz_tafreshi_2018, title={Role of particles spatial distribution in drag reduction performance of superhydrophobic granular coatings}, volume={98}, ISSN={0301-9322}, url={http://dx.doi.org/10.1016/j.ijmultiphaseflow.2017.09.006}, DOI={10.1016/j.ijmultiphaseflow.2017.09.006}, abstractNote={This work presents a detailed computational study on the role of microstructural properties of a superhydrophobic granular coating on its drag reducing performance. More specifically, the effects of the Young–Laplace contact angle, particle diameter, and solid volume fraction on drag reduction are studied for submerged superhydrophobic granular coatings under negative (suction) and positive hydrostatic pressures. In addition, four different particle arrangements (square, staggered, reticulated, and random) are considered to investigate the effects of particle spatial distribution on coatings' drag reduction performance. This was accomplished by accurately predicting the 3-D shape and surface area of a coating's wetted area fraction, and then by using this information to solve the flow field over the coating in a Couette configuration to obtain its drag reduction efficiency. As expected, it was found that drag reduction performance of submerged superhydrophobic coatings decreases with increasing hydrostatic pressure. However, in contrast to coatings comprised of sharp-edged pores, it was found that drag reduction efficiency of granular coatings monotonically increases with decreasing the pressure when the pressure is negative. It was also found that spatial distribution of the particles has no significant effect on drag reduction. The only exception to this conclusion is the case of coatings with reticulated particle packing. Results of our simulations are compared with available data in the literature and discussed in detail.}, journal={International Journal of Multiphase Flow}, publisher={Elsevier BV}, author={Aziz, H. and Tafreshi, H. Vahedi}, year={2018}, month={Jan}, pages={128–138} }
 @article{universal expression for droplet-fiber detachment force_2018, url={https://publons.com/wos-op/publon/2333543/}, DOI={10.1063/1.5032106}, abstractNote={The study reported here is devised to formulate the force required to detach a droplet from a fiber in terms of fiber and droplet physical dimensions and wetting properties. More specifically, a series of experiments were conducted to detach ferrofluid droplets from fibers with different diameters and Young–Laplace contact angles (YLCAs) in a controlled magnetic field and to measure their detachment force. Numerical simulation was conducted to complement the experiment and also to provide validation and insights into the balance of forces acting on a detaching droplet. Our analysis starts with proposing a series of expressions that relate droplet detachment force to its geometrical dimensions at the moment of detachment (at the final equilibrium state before spontaneous detachment). To circumvent the need for conducting experiments or computer simulations to obtain these geometric dimensions, we developed a mathematical relationship that uses an existing set of detachment force data, obtained for an arbitrary droplet–fiber system, to predict the force of detachment for the droplet–fiber system at hand. To further facilitate the use of the above relationship, we used our own data to create an easy-to-use correlation for detachment force. This semi-empirical correlation can be used universally for droplet detachment force prediction without the need for running an experiment or a computer simulation for YLCAs greater than about 20°.}, journal={Journal of Applied Physics}, year={2018} }
 @inproceedings{davoudi_amrei_chase_tafreshi_2017, title={Droplet interactions with smooth and rough fibers}, author={Davoudi, M. and Amrei, M.M. and Chase, G.G. and Tafreshi, H.V.}, year={2017}, month={Apr} }
 @article{amrei_davoudi_chase_tafreshi_2017, title={Effects of roughness on droplet apparent contact angles on a fiber}, volume={180}, ISSN={1383-5866}, url={http://dx.doi.org/10.1016/j.seppur.2017.02.049}, DOI={10.1016/j.seppur.2017.02.049}, abstractNote={This paper reports on our investigation of the effects of surface roughness on the equilibrium shape and apparent contact angles of a droplet deposited on a fiber. In particular, the shape of a droplet on a roughened fiber is studied via the energy minimization method implemented in the surface evolver finite element code. Sinusoidal roughness varying in both the longitudinal and radial directions is considered in the simulations to study the effects of surface roughness on the most stable shape of a droplet on a fiber (corresponding a global minimum energy state). It is found that surface roughness delays droplet shape transition from a symmetric barrel to a clamshell or an asymmetric barrel profile. A phase diagram that includes the effects of fiber roughness on droplet configurations—symmetric barrel, clamshell, and asymmetric barrel—is presented for the first time. It is also found that droplet apparent contact angle tends to decrease on rough fibers. Likewise, roughness tends to increase the force required to detach a droplet from a fiber but the effect diminishes as droplet size increases relative to the size of surface roughness. The results presented in our study have been compared with experimental data or those from prior studies whenever possible, and good agreement has been observed.}, journal={Separation and Purification Technology}, publisher={Elsevier BV}, author={Amrei, M.M. and Davoudi, M. and Chase, G.G. and Tafreshi, H. Vahedi}, year={2017}, month={Jun}, pages={107–113} }
 @article{aziz_amrei_dotivala_tang_tafreshi_2017, title={Modeling Cassie droplets on superhydrophobic coatings with orthogonal fibrous structures}, volume={512}, ISSN={0927-7757}, url={http://dx.doi.org/10.1016/j.colsurfa.2016.10.031}, DOI={10.1016/j.colsurfa.2016.10.031}, abstractNote={Superhydrophobic coatings comprised of orthogonally layered fibers are studied in this paper in terms of their ability to accommodate water droplets in the non-wetting Cassie state. The effects of microstructural properties of these coatings on droplet contact angles and Cassie state stability are investigated via numerical simulation. More specifically, mathematical expressions are derived to predict whether or not such fibrous coatings can provide sufficient capillary forces for the droplet to remain in the Cassie state. For comparison, similar coatings comprised of parallel fibers are also studied, as a droplet may only interact with the first layer of fibers (parallel fibers) when the fiber spacing is smaller than some critical spacing value. Considerable differences were observed between droplet contact angles on coatings made of orthogonally layered fibers and those having multiple layers of parallel fibers. Our numerical simulations conducted using the Surface Evolver finite element code indicated that apparent contact angle of a droplet can be different in longitudinal and transverse directions, and they both increase by decreasing the diameter of the fibers or by increasing their spacing. It was also found that contact angle in the longitudinal direction is more sensitive to the spacing or the diameter of the fibers. It was also found that a droplet may achieve higher contact angles on a coating with orthogonally layered fibers than on its parallel-fiber counterpart.}, journal={Colloids and Surfaces A: Physicochemical and Engineering Aspects}, publisher={Elsevier BV}, author={Aziz, H. and Amrei, M.M. and Dotivala, A. and Tang, C. and Tafreshi, H.Vahedi}, year={2017}, month={Jan}, pages={61–70} }
 @inproceedings{venkateshan_tafreshi_2017, title={Modelling Drag Reduction and Droplet Mobility over Superhydrophobic wire screen}, author={Venkateshan, D.G. and Tafreshi, H.V.}, year={2017}, month={Sep} }
 @inproceedings{amrei_tafreshi_2017, title={Novel Approach to Measuring Droplet Detachment Force from Fibers}, author={Amrei, M.M. and Tafreshi, H.V.}, year={2017}, month={Sep} }
 @article{saleh_tafreshi_pourdeyhimi_2016, title={An analytical approach to predict pressure drop and collection efficiency of dust-load pleated filters}, volume={161}, ISSN={1383-5866}, url={http://dx.doi.org/10.1016/j.seppur.2016.01.034}, DOI={10.1016/j.seppur.2016.01.034}, abstractNote={In this work, a series of first-principle analytical expressions are derived to predict the instantaneous pressure drop and collection efficiency of pleated filters under dust loading condition. Both the depth and surface filtration regimes are formulated for filters with triangular and rectangular pleats. The analytical expressions derived in this paper can be used in the early stages of designing a pleated filter to circumvent the need for conducting CPU-intensive numerical calculations. The predictions of our analytical expressions are compared with those reported in previous studies and good agreement is observed.}, journal={Separation and Purification Technology}, publisher={Elsevier BV}, author={Saleh, A.M. and Tafreshi, H. Vahedi and Pourdeyhimi, B.}, year={2016}, month={Mar}, pages={80–87} }
 @inproceedings{bucher_ameri_tafreshi_2016, title={Electrospun Mats with Orthogonal Fibers for Aerosol Filtration and/or Water Repellency Applications: A Computational Study}, author={Bucher, T.M. and Ameri, M.M. and Tafreshi, H.V.}, year={2016}, month={Sep} }
 @article{venkateshan_amrei_hemeda_cullingsworth_corbett_tafreshi_2016, title={Failure pressures and drag reduction benefits of superhydrophobic wire screens}, volume={511}, ISSN={0927-7757}, url={http://dx.doi.org/10.1016/j.colsurfa.2016.09.087}, DOI={10.1016/j.colsurfa.2016.09.087}, abstractNote={This work presents a detailed study on the failure pressure of spray-coated superhydrophobic wire screens in terms of their geometric and wetting properties. Such information is needed in designing fluid–fluid or fluid–air separation/barrier media as well as drag reducing and self-cleaning surfaces, amongst many others. Good agreement has been observed between the results of our numerical simulations and the experimental data for failure pressure. In addition, the wetted area of the screens was calculated and used to predict their drag reduction benefits when used in a Couette flow configuration under different operating pressures. Interestingly, it was found that operating pressure in the Couette configuration does not significantly affect the drag reducing effects of the screens.}, journal={Colloids and Surfaces A: Physicochemical and Engineering Aspects}, publisher={Elsevier BV}, author={Venkateshan, D.G. and Amrei, M.M and Hemeda, A.A. and Cullingsworth, Z. and Corbett, J. and Tafreshi, H.V.}, year={2016}, month={Dec}, pages={247–254} }
 @article{dodd_tafreshi_tepper_2016, title={Flow-enhanced kinetics of uranyl (UO2) transport into nano-porous silica gel}, volume={106}, ISSN={0264-1275}, url={http://dx.doi.org/10.1016/j.matdes.2016.05.107}, DOI={10.1016/j.matdes.2016.05.107}, abstractNote={Uranyl transport into nanoporous silica gel is limited in a static aqueous solution by slow natural diffusion to the open bonding sites. In order to make this process faster, the diffusion dependence was eliminated using pressure driven fluid flow. Uranyl transport and adsorption within nanoporous silica gel was measured using time-dependent fluorescent measurements in an aqueous solution. The transport kinetics was measured under two different conditions: static solution in a standard cuvette and flowing solution through the silica gel. It was determined that the kinetics of uranyl uptake within nanoporous silica gel depends strongly on the liquid flow velocity. Above a certain velocity, the adsorption kinetics increased by at least two orders of magnitude (from about 40 min to 2 s) in comparison to a static solution. In a static solution, the kinetics depends on the porosity of the silica gel, but this dependence was not observed when the liquid flow velocity exceeded a certain value. Flow-enhanced adsorption kinetics has potential applications for fast detection of trace levels of uranyl in water.}, journal={Materials & Design}, publisher={Elsevier BV}, author={Dodd, Brandon M. and Tafreshi, Hooman V. and Tepper, Gary C.}, year={2016}, month={Sep}, pages={330–335} }
 @article{hemeda_tafreshi_2016, title={Liquid–Infused Surfaces with Trapped Air (LISTA) for Drag Force Reduction}, volume={32}, ISSN={0743-7463 1520-5827}, url={http://dx.doi.org/10.1021/acs.langmuir.5b04754}, DOI={10.1021/acs.langmuir.5b04754}, abstractNote={Superhydrophobic (SHP) surfaces are known for their drag-reducing attributes thanks to their ability to trap air in their surface pores and thereby reduce the contact between water and the frictional solid area. SHP surfaces are prone to failure under elevated pressures or because of air-layer dissolution into the surrounding water. Slippery liquid-infused porous surfaces (SLIPS) or liquid-infused surfaces (LIS) in which the trapped air is replaced with a lubricant have been proposed in the literature as a way of eliminating the air dissolution problem as well as improving the surface stability under pressure. While an LIS surface has been shown to reduce drag for flow of water-glycerol mixture (ref 18), no significant drag reduction has yet been reported for the flow of water (a lower viscosity fluid) over LIS. In this concern, we have designed a new surface in which a layer of air is trapped underneath the infused lubricant to reduce the frictional forces preventing the LIS to provide drag reduction for water or any fluid with a viscosity less than that of the lubricant. Drag reduction performance of such surfaces, referred to here as liquid-infused surfaces with trapped air (LISTA), is predicted by solving the biharmonic equation for the water-oil-air three-phase system in transverse grooves with enhanced meniscus stability thanks to double-reentry designs. For the arbitrary dimensions considered in our proof-of-concept study, LISTA designs showed 20-37% advantage over their LIS counterparts.}, number={12}, journal={Langmuir}, publisher={American Chemical Society (ACS)}, author={Hemeda, A. A. and Tafreshi, H. Vahedi}, year={2016}, month={Mar}, pages={2955–2962} }
 @inproceedings{amrei_tafreshi_2016, title={Modeling Detachment of A Droplet from A Fiber Crossover}, author={Amrei, M.M. and Tafreshi, H.V.}, year={2016}, month={May} }
 @inproceedings{saleh_tafreshi_pourdeyhimi_2016, title={Modeling Filtration Performance of Nanofiber Media, Nanofibers}, author={Saleh, A.M. and Tafreshi, H.V. and Pourdeyhimi, B.}, year={2016}, month={Sep} }
 @inproceedings{saleh_tafreshi_pourdeyhimi_2016, title={Modeling Performance of Pleated Filters under Dust-Loading Condition}, author={Saleh, A. and Tafreshi, H.V. and Pourdeyhimi, B.}, year={2016}, month={May} }
 @inproceedings{ameri_tafreshi_2016, title={Modeling Water Droplet Equilibrium Shape on Fibers with Trilobal Cross-Sections}, author={Ameri, M.M. and Tafreshi, H.V.}, year={2016}, month={Sep} }
 @article{venkateshan_tahir_tafreshi_pourdeyhimi_2016, title={Modeling effects of fiber rigidity on thickness and porosity of virtual electrospun mats}, volume={96}, ISSN={0264-1275}, url={http://dx.doi.org/10.1016/j.matdes.2016.01.105}, DOI={10.1016/j.matdes.2016.01.105}, abstractNote={Despite the widespread applications of electrospun fibers, there is still no accurate method to measure the thickness or porosity of thin electrospun mats. The current study is devised to develop a modeling approach toward solving this problem by simulating the 3-D structure of nanofiber mats. The uniqueness of our algorithm is in its ability to capture how the fibers conform to the geometry of the surface on which they deposit. This feature is important for predicting how the thickness of a nanofiber mat grows as fibers continue to deposit on the collector. Our algorithm is implemented in a C ++ computer program, and is used to study the effects of fiber rigidity, fiber diameter(s), and fiber orientation on the thickness and porosity of electrospun mats. Contrary to the common belief, it was shown that reducing fiber diameter, while maintaining the total weight of the material constant, does not necessarily lead to an increase in the thickness and porosity of the resulting mat. The thickness and porosity of electrospun mats were shown to depend on fibers' tendency to bend at the fiber–fiber crossovers, which may vary depending on the properties of the fibers and the electrospinning process conditions.}, journal={Materials & Design}, publisher={Elsevier BV}, author={Venkateshan, D.G. and Tahir, M.A. and Tafreshi, H.V. and Pourdeyhimi, B.}, year={2016}, month={Apr}, pages={27–35} }
 @article{amrei_venkateshan_d’souza_atulasimha_tafreshi_2016, title={Novel Approach to Measuring the Droplet Detachment Force from Fibers}, volume={32}, ISSN={0743-7463 1520-5827}, url={http://dx.doi.org/10.1021/acs.langmuir.6b03198}, DOI={10.1021/acs.langmuir.6b03198}, abstractNote={Determining the force required to detach a droplet from a fiber or from an assembly of fibers is of great importance to many applications. A novel technique is developed in this work to measure this force experimentally by using ferrofluid droplets in a magnetic field. Unlike previous methods reported in the literature, our technique does not require air flow or a mechanical object to detach the droplet from the fiber(s); therefore, it simplifies the experiment and also allows one to study the capillarity of the droplet-fiber system in a more isolated environment. In this article, we investigated the effects of the relative angle between intersecting fibers on the force required to detach a droplet from the fibers in the in-plane or out-of-plane direction. The in-plane and through-plane detachment forces were also predicted via numerical simulation and compared with the experimental results. Good agreement was observed between the numerical and experimental results. It was found that the relative angle between intersecting fibers has no significant effect on the detachment force in the out-of-plane direction. However, the detachment force in the in-plane direction depends strongly on the relative angle between the fibers, and it increases as this angle increases.}, number={50}, journal={Langmuir}, publisher={American Chemical Society (ACS)}, author={Amrei, M. M. and Venkateshan, D. G. and D’Souza, N. and Atulasimha, J. and Tafreshi, H. Vahedi}, year={2016}, month={Dec}, pages={13333–13339} }
 @inproceedings{tafreshi_2016, title={On the Underwater Performance of Superhydrophobic Fibrous Coatings}, booktitle={American Filtration and Separation Society}, author={Tafreshi, H.V.}, year={2016}, month={May} }
 @inproceedings{venkateshan_yousefi_tahir_tafreshi_pourdeyhimi_2016, title={Structural Simulation of Nanofibrous Materials with Different Fiber Rigidities}, author={Venkateshan, D.G. and Yousefi, S. and Tahir, M.A. and Tafreshi, H.V. and Pourdeyhimi, B.}, year={2016}, month={Sep} }
 @article{hemeda_amrei_tafreshi_2016, title={Wetting states of superhydrophobic surfaces made of polygonal pores or posts}, volume={119}, ISSN={0021-8979 1089-7550}, url={http://dx.doi.org/10.1063/1.4948336}, DOI={10.1063/1.4948336}, abstractNote={In this work, a mathematical framework is developed to describe some of the important intermediate wetting states of a superhydrophobic surface between the two extreme states of Cassie and Wenzel. The superhydrophobic surfaces considered here are comprised of sharp-edged polygonal pores or posts. Two different critical pressures are defined in this work, and used to distinguish pinned, partially pinned, and de-pinned air–water interfaces from one another. This information, in particular, is used to develop predictive expressions for the critical pressure and wetted area of the surfaces. Good agreement is observed between the predictions of our expressions and those obtained from numerical calculations or experiment. The work presented here compares the pressure-dependent performances of the superhydrophobic surfaces having different pore or post designs with one another.}, number={17}, journal={Journal of Applied Physics}, publisher={AIP Publishing}, author={Hemeda, A. A. and Amrei, M. M. and Tafreshi, H.V.}, year={2016}, month={May}, pages={175304} }
 @article{amrei_tafreshi_2015, title={Effects of hydrostatic pressure on wetted area of submerged superhydrophobic granular coatings. Part 1: mono-dispersed coatings}, volume={465}, ISSN={0927-7757}, url={http://dx.doi.org/10.1016/j.colsurfa.2014.10.032}, DOI={10.1016/j.colsurfa.2014.10.032}, abstractNote={Abstract Properly designed superhydrophobic surfaces can reduce the skin-friction drag on objects submerged in moving water. This drag reduction is caused by a reduction in wetted area from air entrapped in the pores of the surface. For granular superhydrophobic surfaces, where the air–water interface is not necessarily pinned to the pore entrance, predicting the wetted area is not a trivial task, as the air–water interface can easily move into or out of the pore in response to instantaneous operating pressure or due to air dissolution into the ambient water. The relationship between wetted area and drag-reduction is complicated, and reducing the wetted area does not guarantee a reduction in drag force. However, the ability to predict the wetted area allows one to design more efficient superhydrophobic coatings to meet the specific needs of different applications. This work presents an analytical force-balance method developed to approximate the wetted area of a superhydrophobic surface made of particles of equal size but different Young–Laplace contact angles. The accuracy of our simple analytical formulations is examined using the rigorous numerical calculations of the Surface Evolver code, and reasonable agreement has been observed. Effects of particle diameter, particle contact angles, particle packing fraction, and spatial distribution on positive and negative critical hydrostatic pressures and their corresponding wetted area are predicted and discussed in detail.}, journal={Colloids and Surfaces A: Physicochemical and Engineering Aspects}, publisher={Elsevier BV}, author={Amrei, M.M. and Tafreshi, H. Vahedi}, year={2015}, month={Jan}, pages={87–98} }
 @article{amrei_tafreshi_2015, title={Effects of pressure on wetted area of submerged superhydrophobic granular coatings. Part II: poly-dispersed coatings}, volume={481}, ISSN={0927-7757}, url={http://dx.doi.org/10.1016/j.colsurfa.2015.05.030}, DOI={10.1016/j.colsurfa.2015.05.030}, abstractNote={The effects of hydrostatic pressure on the stability of the air–water interface over submerged superhydrophobic coatings comprised of mono-dispersed particles was studied in the first part of this two-part publication [Colloids and Surfaces A, 465 (2015) 87–98]. In this second part, our formulations are extended to cover granular coatings comprised of randomly arranged particles having bi-dispersed or poly-dispersed size and contact angle distributions. Simple analytical formulations are developed to predict how the air–water interface transitions from a non-wetted (Cassie) state to the fully-wetted (Wenzel) state through a series of intermediate wetting states. In particular, a simple mono-dispersed equivalent particle diameter is proposed to be used in predicting the critical pressure and wetted area of poly-dispersed coatings comprised of particles of different diameters and contact angles as a function of hydrostatic pressure. Numerical simulations conducted via the Surface Evolver finite element code have been used to examine the accuracy of the analytical formulations developed in this study.}, journal={Colloids and Surfaces A: Physicochemical and Engineering Aspects}, publisher={Elsevier BV}, author={Amrei, M.M. and Tafreshi, H. Vahedi}, year={2015}, month={Sep}, pages={547–560} }
 @inproceedings{hemeda_tafreshi_2015, title={Instantaneous Slip Length in Superhydrophobic Microchannels}, author={Hemeda, A.A. and Tafreshi, H.V.}, year={2015}, month={Nov} }
 @article{hemeda_tafreshi_2015, title={Instantaneous slip length in superhydrophobic microchannels having grooves with curved or dissimilar walls}, volume={27}, ISSN={1070-6631 1089-7666}, url={http://dx.doi.org/10.1063/1.4931588}, DOI={10.1063/1.4931588}, abstractNote={Superhydrophobic (SHP) surfaces can be used to reduce the skin-friction drag in a microchannel. This is due to the peculiar ability of these surfaces to entrap air in their pores and thereby reduce the contact area between water and the solid surface. The favorable drag-reduction effect, however, can quickly deteriorate if the surface geometry is not designed properly. The deterioration can be sudden, caused by exposure to excessive pressures, or gradual, due to the dissolution of the entrapped air into the ambient water. The formulations presented here provide a means for studying the time-dependent drag-reduction in a microchannel enhanced with transverse or longitudinal SHP grooves of varying wall profiles or wettabilities. Moreover, different mathematical approaches are developed to distinguish the performance of a sharp-edged groove from that of a groove with round entrance. The work starts by deriving an equation for the balance of forces on the air–water interface (AWI) inside a groove and solving this differential equation, along with Henry’s law, for the rate of dissolution of the entrapped air into water over time. It was shown that the performance of a SHP groove depends mostly on the interplay between the effects of the apparent contact angle of the AWI and the initial volume of the groove. The instantaneous slip length is then calculated by solving the Navier–Stokes equations for flow in microchannels with SHP grooves. Our results are compared with the studies in the literature whenever available, and good agreement has been observed.}, number={10}, journal={Physics of Fluids}, publisher={AIP Publishing}, author={Hemeda, A. A. and Tafreshi, H.V.}, year={2015}, month={Oct}, pages={102101} }
 @inproceedings{bucher_tafreshi_2015, title={Modeling Fluid Penetration in Fibrous Media with Heterogeneous Wettabilities}, author={Bucher, T.M. and Tafreshi, H.V.}, year={2015}, month={Apr} }
 @article{saleh_tafreshi_2015, title={On the filtration performance of dust-loaded trilobal fibers}, volume={149}, ISSN={1383-5866}, url={http://dx.doi.org/10.1016/j.seppur.2015.06.005}, DOI={10.1016/j.seppur.2015.06.005}, abstractNote={This paper is prepared to shed some light on the filtration performance of fibers with trilobal cross-section in comparison to their circular counterparts when loaded with aerosol particles. A trilobal geometry consisting of three overlapping elliptical lobes with major and minor diameters of 8 and 4 μm, and a particle diameter range of 0.125–2 μm are considered as representative examples of fibers and particles of a common aerosol filtration application. The results reported in this paper are obtained using micro- and macroscale simulation methods that we previously developed for modeling unsteady-state dust-cake formation inside and outside fibrous filters. Different flow velocities are considered to discuss performance of trilobal fibers under different particle capture regimes. For the range of particle and fiber diameters considered, the trilobal fibers are found to outperform their circular counterparts only when the particles are highly inertial, and only if the orientation of the trilobal cross-section with respect to the incoming flow is such that one of the grooves of the fiber faces the flow with a normal angle. This is in agreement with our previous simulations of clean trilobal fibers. In the case of low inertial particles, trilobal fibers were found to exhibit a higher efficiency with loading but at the expense of a significantly higher pressure drop. With the lack of perfect control over how the grooves will be oriented in a fibrous filter, one may conjecture that, other parameters being constant, the probability of an aerosol filter comprised of trilobal fibers performing better than its counterpart made of circular fibers is not very high. We also studied the effects of the through-plane orientation of the trilobal fibers on their performance relative to their circular counterpart. Similar conclusions were drawn from the latter simulations.}, journal={Separation and Purification Technology}, publisher={Elsevier BV}, author={Saleh, A.M. and Tafreshi, H.V.}, year={2015}, month={Jul}, pages={295–307} }
 @article{saleh_tafreshi_pourdeyhimi_2015, title={Service life of circular pleated filters vs. that of their flat counterpart}, volume={156}, ISSN={1383-5866}, url={http://dx.doi.org/10.1016/j.seppur.2015.09.041}, DOI={10.1016/j.seppur.2015.09.041}, abstractNote={In this note, an easy-to-use two-dimensional model is developed to predict the instantaneous pressure drop and collection efficiency of circular pleated filters as a function of time in both the surface and depth filtration regimes. Our model uses average velocity profiles that represent the flow field inside a circular pleated filter to circumvent the need for conducting CPU-intensive CFD calculations to predict the service life of a circular filter. This is accomplished by considering a reasonable dust-cake profile inside the pleat channels as a function of the flow and particles properties, and allowing the cake to grow as the filter continues to collect particles over time. Despite the approximate nature of its predictions, the speed at which a large parameter study can be completed makes the present model very valuable for design and development of circular pleated filters. Using this model for instance, it can be shown quantitatively that circular filters with high inlet-to-outlet diameter ratios outperform their flat counterparts.}, journal={Separation and Purification Technology}, publisher={Elsevier BV}, author={Saleh, A.M. and Tafreshi, H. Vahedi and Pourdeyhimi, B.}, year={2015}, month={Dec}, pages={881–888} }
 @inproceedings{tafreshi_hemeda_2015, title={Submerged Superhydrophobic Surfaces with Partially-Pinned Air-Water Interface}, author={Tafreshi, H.V. and Hemeda, A.}, year={2015}, month={Nov} }
 @inproceedings{bucher_tafreshi_2015, title={Water Entry Pressure for Heterogeneous Superhydrophobic Fibrous Materials}, author={Bucher, T.M. and Tafreshi, H.V.}, year={2015}, month={Apr} }
 @article{bucher_amrei_tafreshi_2015, title={Wetting resistance of heterogeneous superhydrophobic coatings with orthogonally layered fibers}, volume={277}, ISSN={0257-8972}, url={http://dx.doi.org/10.1016/j.surfcoat.2015.07.032}, DOI={10.1016/j.surfcoat.2015.07.032}, abstractNote={Superhydrophobic coatings comprised of electrospun nanofibers are a low-cost alternative to micro-fabricated surfaces, and can be applied to substrates of any arbitrary geometry. Such coatings with orthogonally oriented layers have properties that allow their wetting resistance to be predictable for a range of solid volume fractions, fiber diameters, and contact angles. In this paper, we have presented a modeling strategy that solves for the air–water interface shape over several layers of such coatings to predict the resistance of superhydrophobic fiber coatings to hydrostatic pressures and to quantify the relationship between microstructure, meniscus penetration depth, and wetted surface area of the fibers. Slip length predictions are also provided to shed some light on the performance of such coatings in drag reduction applications. It was found that while failure pressure for a coating rises with reducing fiber spacing, there is a tradeoff with wetted fiber surface area relative to a bare substrate. This tradeoff can be offset, however, by using smaller fibers for an intended coating. This results in a higher failure pressure for the same wetted area fraction. The results generated in this work are discussed in relation to those reported in the literature whenever possible.}, journal={Surface and Coatings Technology}, publisher={Elsevier BV}, author={Bucher, T.M. and Amrei, M.M. and Tafreshi, H.V.}, year={2015}, month={Sep}, pages={117–127} }
 @article{saleh_vahedi tafreshi_2014, title={A simple semi-numerical model for designing pleated air filters under dust loading}, volume={137}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84908463218&partnerID=MN8TOARS}, DOI={10.1016/j.seppur.2014.09.029}, abstractNote={In this work, we present a semi-numerical 2-D model for predicting the instantaneous pressure drop and collection efficiency of filters made up of rectangular and triangular pleats in both depth and surface filtration regimes. Inspired from previous CFD simulations, our semi-numerical model adopts appropriate average velocity profiles in the axial and lateral directions to approximate the flow field inside rectangular and triangular pleat channels. The model therefore circumvents the need to obtain a CPU-intensive solution for the partial differential equations governing the flow through a filter, i.e., Navier–Stokes equations. The above-mentioned analytical flow field can then be used to predict the trajectory of the particles flowing through the pleat channels by numerically solving the equation of motion for each particle—a simple set of second order ordinary differential equations. With the particles trajectories obtained, the deposition location and so the dust-cake profile can be approximated. This allows one to predict the instantaneous pressure drop and collection efficiency of a filter (filter’s service life) with a CPU-time of practically zero min. The model developed in this work is aimed at providing the aerosol filtration industry with a fast, but yet fairly accurate method of designing pleated filters. A brief parametric study is presented for model demonstration. In addition, a comparison between the predictions of our model and some experimental data from literature is presented for completeness of the study.}, journal={Separation and Purification Technology}, author={Saleh, A.M. and Vahedi Tafreshi, H.}, year={2014}, pages={94–108} }
 @article{hemeda_gad-el-hak_tafreshi_2014, title={Effects of hierarchical features on longevity of submerged superhydrophobic surfaces with parallel grooves}, volume={26}, ISSN={1070-6631 1089-7666}, url={http://dx.doi.org/10.1063/1.4891363}, DOI={10.1063/1.4891363}, abstractNote={While the air–water interface over superhydrophobic surfaces decorated with hierarchical micro- or nanosized geometrical features have shown improved stability under elevated pressures, their underwater longevity—-the time that it takes for the surface to transition to the Wenzel state—-has not been studied. The current work is devised to study the effects of such hierarchical features on the longevity of superhydrophobic surfaces. For the sake of simplicity, our study is limited to superhydrophobic surfaces composed of parallel grooves with side fins. The effects of fins on the critical pressure—-the pressure at which the surface starts transitioning to the Wenzel state—-and longevity are predicted using a mathematical approach based on the balance of forces across the air–water interface. Our results quantitatively demonstrate that the addition of hierarchical fins significantly improves the mechanical stability of the air–water interface, due to the high advancing contact angles that can be achieved when an interface comes in contact with the fins sharp corners. For longevity on the contrary, the hierarchical fins were only effective at hydrostatic pressures below the critical pressure of the original smooth-walled groove. Our results indicate that increasing the length of the fins decreases the critical pressure of a submerged superhydrophobic groove but increases its longevity. Increasing the thickness of the fins can improve both the critical pressure and longevity of a submerged groove. The mathematical framework presented in this paper can be used to custom-design superhydrophobic surfaces for different applications.}, number={8}, journal={Physics of Fluids}, publisher={AIP Publishing}, author={Hemeda, A. A. and Gad-el-Hak, M. and Tafreshi, H. Vahedi}, year={2014}, month={Aug}, pages={082103} }
 @article{hemeda_tafreshi_2014, title={General Formulations for Predicting Longevity of Submerged Superhydrophobic Surfaces Composed of Pores or Posts}, volume={30}, ISSN={0743-7463 1520-5827}, url={http://dx.doi.org/10.1021/la501894u}, DOI={10.1021/la501894u}, abstractNote={Superhydrophobicity can arise from the ability of a submerged rough hydrophobic surface to trap air in its surface pores, and thereby reduce the contact area between the water and the frictional solid walls. A submerged surface can only remain superhydrophobic (SHP) as long as it retains the air in its pores. SHP surfaces have a short underwater life, and their longevity depends strongly on the hydrostatic pressure at which they operate. In this work, a comprehensive mathematical framework is developed to predict the mechanical stability and the longevity of submerged SHP surfaces with arbitrary pore or post geometries. We start by deriving an integro-partial differential equation for the 3-D shape of the air-water interface, and use this information to predict the rate of dissolution of the entrapped air into the ambient water under different hydrostatic pressures. For the special case of circular pores, the above integro-partial differential equation is reduced to easy-to-solve ordinary differential equations. In addition, approximate nonlinear algebraic solutions are also obtained for surfaces with circular pores or posts. The effects of geometrical parameters and hydrostatic conditions on surface stability and longevity are discussed in detail. Moreover, a simple equivalent pore diameter method is developed for SHP surfaces composed of posts with ordered or random configuration--an otherwise complicated task requiring the solution of an integro-partial differential equation.}, number={34}, journal={Langmuir}, publisher={American Chemical Society (ACS)}, author={Hemeda, A. A. and Tafreshi, H. Vahedi}, year={2014}, month={Aug}, pages={10317–10327} }
 @article{bucher_vahedi tafreshi_2014, title={Modeling air-water interface in disordered fibrous media with heterogeneous wettabilities}, volume={461}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84906769865&partnerID=MN8TOARS}, DOI={10.1016/j.colsurfa.2014.08.006}, abstractNote={Considering the balance of mechanical forces across a meniscus anchored to two circular objects, we developed a CPU-friendly semi-analytical algorithm for tracking the instantaneous shape and position of the air–water interface inside microstructures that resemble a collection of disordered parallel cylinders, e.g., a bundle of fibers in a fiber-reinforced composite or microfabricated posts in a microfluidic system. In the context of fluid transport in fibrous media, in particular, the methodology presented in this paper provides a means for producing a relationship between capillary pressure and fluid saturation in media with heterogeneous wettabilities – often needed to predict the rate of fluid transport. In addition, we developed a conversion formulation that allows a capillary pressure–saturation relationship obtained for one combination of contact angles to be used to construct such a relationship for media with different combinations of contact angles, eliminating the need for additional simulations.}, number={1}, journal={Colloids and Surfaces A: Physicochemical and Engineering Aspects}, author={Bucher, T.M. and Vahedi Tafreshi, H.}, year={2014}, pages={323–335} }
 @article{arambakam_tafreshi_pourdeyhimi_2014, title={Modeling performance of multi-component fibrous insulations against conductive and radiative heat transfer}, volume={71}, ISSN={0017-9310}, url={http://dx.doi.org/10.1016/j.ijheatmasstransfer.2013.12.031}, DOI={10.1016/j.ijheatmasstransfer.2013.12.031}, abstractNote={In this work, we present a simulation methodology for studying heat transfer in multi-component fibrous media. Our simulation method is designed for high-porosity insulation media with air as the interstitial fluid where conduction through the solid structure is minimal. We obtain the resistance of fibrous media to radiative heat via a simulation method that incorporates both the microscale (fiber-level) and macroscale (media-level) properties of the constituent materials. We then combine this information with that obtained analytically for the conduction heat transfer through the media. The method presented here allows one to obtain quantitative predictions for the performance of media made up of different combinations of fibers with different materials or dimensions. For validation purposes, we simulated the experiment of Houston and Korpela [28] which was conducted for glass fiber insulations, and observed good agreement between the measurements and our predictions. For further demonstration, insulation media made up of glass and mineral wools fibers with different mass fractions and fiber diameters are simulated in blend and layered configurations and compared with each other. It was found that layered and blended fibrous multi-component insulations exhibit similar performance. It was also found that the stacking sequence does not affect the thermal resistance of layered media for the range of parameters studied here, in agreement with previous studies.}, journal={International Journal of Heat and Mass Transfer}, publisher={Elsevier BV}, author={Arambakam, R. and Tafreshi, H. Vahedi and Pourdeyhimi, B.}, year={2014}, month={Apr}, pages={341–348} }
 @article{saleh_fotovati_tafreshi_pourdeyhimi_2014, title={Modeling service life of pleated filters exposed to poly-dispersed aerosols}, volume={266}, ISSN={["1873-328X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84903575710&partnerID=MN8TOARS}, DOI={10.1016/j.powtec.2014.06.011}, abstractNote={In this work, we present a fast and flexible 3-D macroscale simulation method for modeling the instantaneous pressure drop and collection efficiency of pleated fibrous filters when exposed to poly-dispersed aerosols in both surface and depth filtration regimes. The simulations are conducted using the Fluent CFD code enhanced with a series of in-house subroutines. A cluster-injection method is developed to accelerate the formation and growth of dust-cake both inside and outside the filter media. Once calibrated with experiment or more accurate microscale simulations, the cluster-injection method can be used to simulate the service life of a pleated filter with reasonable accuracy and CPU time. The simulation methodology developed in this work can be used to design and develop pleated filters for different applications. In particular, it allows one to study the effects of pleat shape, pleat count, filter porosity, fiber diameter(s), flow velocity, aerosol concentration, and particle diameter, as well as the aerodynamic parameters of the flow on the evolution of a filter's pressure drop and collection efficiency over time. For demonstration purposes, performance of an arbitrary filter with 2 and 4 pleats per inch is simulated when challenged with poly-dispersed particles of 1 to 10 μm in diameter. For the filter simulated here, it was found that exposure to the above poly-dispersed aerosols results in a shorter service life in comparison to when the filter is exposure to mono-dispersed aerosols with a diameter of 1 or 10 μm having the same mass flux.}, journal={POWDER TECHNOLOGY}, author={Saleh, A. M. and Fotovati, S. and Tafreshi, H. Vahedi and Pourdeyhimi, B.}, year={2014}, month={Nov}, pages={79–89} }
 @article{saleh_hosseini_vahedi tafreshi_pourdeyhimi_2013, title={3-D microscale simulation of dust-loading in thin flat-sheet filters: A comparison with 1-D macroscale simulations}, volume={99}, ISSN={0009-2509}, url={http://dx.doi.org/10.1016/J.CES.2013.06.007}, DOI={10.1016/j.ces.2013.06.007}, abstractNote={In this work, a microscale approach is undertaken to simulate the instantaneous pressure drop and collection efficiency of fibrous media exposed to particle loading, i.e., filter aging. The air flow field through 3-D disordered geometries representing the internal microstructure of a fibrous filter is obtained by numerically solving Stokes' equations. A Lagrangian approach is used to track the trajectory of particles through our virtual filter media and determine the filter's collection efficiency under different dust-load conditions. The calculations were conducted using the ANSYS CFD code enhanced with a series of in-house C++ subroutines. To better illustrate the value of such CPU-intensive 3-D microscale modeling, we compared the results of our simulations with those obtained from a 1-D macroscale model developed based on some of the pioneering studies reported in the literature. It was found that while the 1-D macroscale models can provide fast predictions for the pressure drop and collection efficiency of a given filter, they require a series of empirical correction factors or case-specific assumptions that limit their usage for design and development of new filter media. The 3-D microscale simulation methods, in contrast, are self-sufficient as they are developed based on first principles. With the current rate of progress in developing high-speed computers, it is expected that 3-D microscale simulations will be the preferred method of filter design in the near future.}, journal={Chemical Engineering Science}, publisher={Elsevier BV}, author={Saleh, A.M. and Hosseini, S.A. and Vahedi Tafreshi, H. and Pourdeyhimi, B.}, year={2013}, month={Aug}, pages={284–291} }
 @article{arambakam_vahedi tafreshi_pourdeyhimi_2013, title={A simple simulation method for designing fibrous insulation materials}, volume={44}, ISSN={0261-3069}, url={http://dx.doi.org/10.1016/j.matdes.2012.07.058}, DOI={10.1016/j.matdes.2012.07.058}, abstractNote={Conductive heat in a fibrous material travels through both the air (interstitial fluid) and the fibers (solid phase). The numerical simulations reported in this paper are devised to study the effective thermal conductivity of fibrous media with different microstructural parameters. Simulations were conducted in 3-D fibrous geometries resembling the microstructure of a fibrous material. Assuming that the heat transfer through the interstitial fluid is independent of the geometrical parameters of the solid phase (for when the porosity is held constant), the energy equation was solved only for the solid structures, and the resulting values were used to predict the effective thermal conductivity of the whole media. This treatment allows us to drastically reduce the computational cost of such simulations. The results indicate that heat conduction through the solid fibrous structure increases by increasing the material's solid volume fraction, fiber diameter, and fibers' through-plane orientations. The in-plane orientation of the fibers, on the other hand, did not show any significant influence on the material's conductivity. It was also shown that the microstructural parameters of fibrous insulations have negligible influence on the material's performance if the conductivity of the solid phase is close to that of the interstitial fluid.}, journal={Materials & Design}, publisher={Elsevier BV}, author={Arambakam, R. and Vahedi Tafreshi, H. and Pourdeyhimi, B.}, year={2013}, month={Feb}, pages={99–106} }
 @article{barth_tafreshi_gad-el-hak_2013, title={Convective Air Mass Transfer in Submerged Superhydrophobic Surfaces: Turbulent Flow}, volume={58}, ISSN={0003-0503}, number={18}, journal={Bulletin of the American Physical Society}, author={Barth, C.A. and Tafreshi, H.V. and Gad-el-Hak, M.}, year={2013}, pages={349} }
 @article{barth_samaha_tafreshi_gad-el-hak_2013, title={Convective Mass Transfer From Submerged Superhydrophobic Surfaces}, volume={5}, ISSN={1756-8250}, url={http://dx.doi.org/10.1260/1756-8250.5.2.79}, DOI={10.1260/1756-8250.5.2.79}, abstractNote={Longevity of entrapped air is an outstanding problem for using superhydrophobic coatings in submersible applications. Under pressure and flowing water, the air micropockets eventually dissolve into the ambient water or burst and diminish. Herein, we analyze from first principles a simple mass transfer problem. We introduce an effective slip to a Blasius boundary layer, and solve the hydrodynamic equations. A slowly evolving, non-similar solution is found. We then introduce the hydrodynamic solution to the two-dimensional problem of alternating solid-water and air-water interfaces to determine the convective mass transfer of air's dissolution into water. This situation simulates spanwise microridges, which is one of the geometries used for producing superhydrophobic surfaces. The mass-transfer problem has no similarity solution but is solvable using approximate integral methods. A mass-transfer solution is achieved as a function of the surface geometry (or gas area fraction), Reynolds number, and Schmidt n...}, number={2}, journal={International Journal of Flow Control}, publisher={Portico}, author={Barth, Christina and Samaha, Mohamed and Tafreshi, Hooman and Gad-el-Hak, Mohamed}, year={2013}, month={Jun}, pages={79–88} }
 @article{barth_samaha_tafreshi_gad-el-hak_2013, title={Convective Mass Transfer From Submerged Superhydrophobic Surfaces: Turbulent Flow}, volume={5}, ISSN={1756-8250}, url={http://dx.doi.org/10.1260/1756-8250.5.3-4.143}, DOI={10.1260/1756-8250.5.3-4.143}, abstractNote={Superhydrophobic surfaces have received considerable attention in recent years. The surface has a strong water-repellent characteristic that could produce slip flow and drag reduction. The coating traps air within its micropores, such that a submerged moving body experiences shear-free and no-slip regions over, respectively, the air pockets and the solid surface. This, in turn, holds promise for a broad range of applications. Longevity of the entrapped air is an outstanding problem for these coatings. Under pressure and flowing water, the air micropockets eventually dissolve into the ambient water or burst and diminish. Herein, we analyze from first principles an air mass transfer problem. Using integral methods, we extend our prior laminar flow solution to turbulent flows. We introduce an effective slip to the turbulent boundary layer characterized by a modified 1/7-power law velocity profile. We then introduce the hydrodynamic solution to the two-dimensional problem of alternating solid-water and air-wa...}, number={3-4}, journal={International Journal of Flow Control}, publisher={Portico}, author={Barth, Christina and Samaha, Mohamed and Tafreshi, Hooman and Gad-el-Hak, Mohamed}, year={2013}, month={Sep}, pages={143–152} }
 @article{arambakam_tafreshi_pourdeyhimi_2013, title={Dual-scale 3-D approach for modeling radiative heat transfer in fibrous insulations}, volume={64}, ISSN={0017-9310}, url={http://dx.doi.org/10.1016/j.ijheatmasstransfer.2013.05.047}, DOI={10.1016/j.ijheatmasstransfer.2013.05.047}, abstractNote={Abstract In this work, a dual-scale computationally-affordable 3-D method is developed to simulate the transfer of radiative heat through fibrous media comprised of fibers with different diameters and orientations. The simulations start by generating a virtual fibrous material with specified microstructural properties and then compute the radiative properties of each fiber (i.e., effective phase function, as well as scattering and absorption coefficients) in the structure using the Mie Scattering theory. Considering independent scattering formulations for our fibrous media (media with high porosities), the radiative properties of the insulation material are computed by summing up the radiative properties of each individual fiber, after transforming the phase function values from the fiber’s local 3-D coordinates system to a fixed global coordinates system. The radiative properties of the media are then used in the Radiative Transfer Equation (RTE) equation, an integro-differential equation obtained for computing the attenuation and augmentation of an InfraRed ray’s energy as it travels through a fibrous medium. Using the Discrete Ordinate Method (DOM), the RTE is then discretized into a system of twenty four coupled partial differential equations and solved numerically using the FlexPDE program to obtain the rate of heat transfer through the entire thickness of the media. Studying media with different microstructural properties, it was quantitatively shown that increasing solid volume fraction, thickness, or fibers’ through-plane orientation increases the rate of heat transfer through insulation. With regard to the role of fiber diameter, it was found that there exists a fiber diameter for which radiation heat transfer through a fibrous media is minimal, ranging between 3 and 10 μm for glass fibers operating in a temperature range of about 340–750 K.}, journal={International Journal of Heat and Mass Transfer}, publisher={Elsevier BV}, author={Arambakam, R. and Tafreshi, H. Vahedi and Pourdeyhimi, B.}, year={2013}, month={Sep}, pages={1109–1117} }
 @inproceedings{fotovati_saleh_tafreshi_pourdeyhimi_2013, title={Modeling Depth and Surface Dust-Loading in Pleated Air Filters}, author={Fotovati, S. and Saleh, A. and Tafreshi, H.V. and Pourdeyhimi, B.}, year={2013}, month={May} }
 @article{bucher_tafreshi_tepper_2013, title={Modeling performance of thin fibrous coatings with orthogonally layered nanofibers for improved aerosol filtration}, volume={249}, ISSN={0032-5910}, url={http://dx.doi.org/10.1016/j.powtec.2013.07.023}, DOI={10.1016/j.powtec.2013.07.023}, abstractNote={Advances in nanofiber fabrication techniques (e.g., electrospinning) have come to allow control over fiber distribution and orientation such that an ordered coating with fibers arranged in layers orthogonal to one another can potentially be produced. Such coatings can serve as a nano-sieve that can be designed and placed on the downstream side of a conventional nonwoven fibrous filter to enhance its performance (collection efficiency for a given pressure drop). This paper presents a thorough analysis of the performance characteristics of these thin coatings to guide the fabrication process in terms of the coatings' microstructural properties. In particular, we have found a correlation such that, for coatings composed of a given fiber size, there exists a corresponding particle size for which a coating's performance becomes independent of variations in fiber-to-fiber spacing (i.e., coating's non-homogeneity). We have also found that a coating's performance improves when its mass is distributed across more than one pair of orthogonal layers.}, journal={Powder Technology}, publisher={Elsevier BV}, author={Bucher, T.M. and Tafreshi, H. Vahedi and Tepper, G.C.}, year={2013}, month={Nov}, pages={43–53} }
 @article{samaha_vahedi tafreshi_gad-el-hak_2013, title={Novel method to characterize superhydrophobic coatings}, volume={395}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84875504535&partnerID=MN8TOARS}, DOI={10.1016/j.jcis.2012.12.066}, abstractNote={Superhydrophobic coatings possess a strong water-repellent characteristic, which, among several other potential applications, enhances the mobility of water droplets over the surface. The coating traps air within its micropores, such that a submerged moving body experiences shear-free and no-slip regions over, respectively, the air pockets and the solid surface. This, in turn, may lead to significant skin-friction reduction. The coating maintains its superhydrophobicity as long as the air remains entrapped. It is therefore of great interest to precisely measure the amount of trapped air, which is particularly difficult to estimate for coatings with disordered microstructures. A novel method to measure the effective thickness and gas volume fraction of superhydrophobic coatings with either ordered or random microroughness is advanced. The technique is applied to both aerogel and electrospun fibrous coatings. The experiments utilize a sensitive weighing scale (down to 10−4 gm) and height gauge (down to 10 μm) to determine the buoyancy force on an immersed, coated glass-slide substrate. The measured force is used to calculate the volume fraction of entrapped air. The coating’s effective thickness also follows from the same calculations. The sensitivity of our particular scale enables the measuring of thicknesses down to 3 μm, which is not readily possible with conventional thickness gauges. Smaller thicknesses could be measured using more sensitive scales.}, number={1}, journal={Journal of Colloid and Interface Science}, author={Samaha, M.A. and Vahedi Tafreshi, H. and Gad-el-Hak, M.}, year={2013}, pages={315–321} }
 @article{bucher_vahedi tafreshi_2013, title={On applications and limitations of one-dimensional capillarity formulations for media with heterogeneous wettability}, volume={102}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84879824357&partnerID=MN8TOARS}, DOI={10.1063/1.4811167}, abstractNote={Force-balance-based one-dimensional algebraic formulations that are often used in characterizing the capillarity of a multi-component system (e.g., predicting capillary height rise in porous media) are discussed. It is shown that such formulations fail to provide accurate predictions when the distribution of wetting (or non-wetting) surfaces is not homogeneous. A more general mathematical formulation is suggested and used to demonstrate that for media with heterogeneous wettability, hydrophilic (or hydrophobic) surfaces clustered in groups will have less contribution to the overall capillarity of the system.}, number={24}, journal={Applied Physics Letters}, author={Bucher, T.M. and Vahedi Tafreshi, H.}, year={2013} }
 @article{emami_fotovati_amrei_tafreshi_2013, title={On the effects of fiber orientation in permeability of fibrous media to power-law fluids}, volume={60}, ISSN={0017-9310}, url={http://dx.doi.org/10.1016/j.ijheatmasstransfer.2013.01.025}, DOI={10.1016/j.ijheatmasstransfer.2013.01.025}, abstractNote={In this note, for the first time, the flow of power-law fluids is numerically simulated in 3-D fibrous structures resembling the internal microstructure of fibrous hygiene products to study the effects of fibers’ in-plane and through-plane orientations on the media’s permeability. It was found that while the permeability of a fibrous material to a power-law fluid hardly depends on the in-plane orientation of the fibers, it increases with increasing the fibers’ through-plane orientation. Moreover, we developed a simple analytical expression that can be used together with the empirical correlation of Davies (1973) [16], modified with an equation derived by Banks (1987) [17], to predict the permeability of anisotropic fibrous media to power-law non-Newtonian fluids. The predictions of our formulation are compared with our numerical simulations and good agreement is observed.}, journal={International Journal of Heat and Mass Transfer}, publisher={Elsevier BV}, author={Emami, B. and Fotovati, S. and Amrei, M.M. and Tafreshi, H. Vahedi}, year={2013}, month={May}, pages={375–379} }
 @article{emami_hemeda_amrei_luzar_gad-el-hak_vahedi tafreshi_2013, title={Predicting longevity of submerged superhydrophobic surfaces with parallel grooves}, volume={25}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84880126879&partnerID=MN8TOARS}, DOI={10.1063/1.4811830}, abstractNote={A mathematical framework is developed to predict the longevity of a submerged superhydrophobic surface made up of parallel grooves. Time-dependent integro-differential equations predicting the instantaneous behavior of the air–water interface are derived by applying the balance of forces across the air–water interface, while accounting for the dissolution of the air in water over time. The calculations start by producing a differential equation for the initial steady-state shape and equilibrium position of the air–water interface at t = 0. Analytical and/or numerical solutions are then developed to solve the time-dependent equations and to compute the volume of the trapped air in the grooves over time until a Wenzel state is reached as the interface touches the groove's bottom. For demonstration, a superhydrophobic surface made of parallel grooves is considered, and the influence of the groove's dimensions on the longevity of the surface under different hydrostatic pressures is studied. It was found that for grooves with higher width-to-depth ratios, the critical pressure (pressure at which departure from the Cassie state starts) is higher due to stronger resistance to deflection of the air–water interface from the air trapped in such grooves. However, grooves with higher width-to-depth ratios reach the Wenzel state faster because of their greater air–water interface areas.}, number={6}, journal={Physics of Fluids}, author={Emami, B. and Hemeda, A.A. and Amrei, M.M. and Luzar, A. and Gad-el-Hak, M. and Vahedi Tafreshi, H.}, year={2013} }
 @article{fotovati_tafreshi_pourdeyhimi_2012, title={A macroscale model for simulating pressure drop and collection efficiency of pleated filters over time}, volume={98}, ISSN={1383-5866}, url={http://dx.doi.org/10.1016/j.seppur.2012.07.009}, DOI={10.1016/j.seppur.2012.07.009}, abstractNote={In this work, a computationally affordable macroscale model is developed to simulate the instantaneous collection efficiency and pressure drop of pleated depth filters. The numerical scheme presented here allows for the deposition of particles inside the fibrous fabric of a pleated filter, and accordingly varies its permeability and capture efficiency to simulate aging of the filter over time. This has been accomplished by developing a series of in-house subroutines that remarkably enhance the capabilities of the commercially available computational fluid dynamics code from ANSYS. This model is used to quantify the influence of pleat count, particle diameter, and flow velocity on the instantaneous performance of pleated filters with V-shaped pleats. Our results indicate that increasing the number of pleats reduces the rate of increase of a filter's pressure drop and capture efficiency. Predictions of our model have been compared against available experimental data, and good agreement has been observed.}, journal={Separation and Purification Technology}, publisher={Elsevier BV}, author={Fotovati, S. and Tafreshi, H. Vahedi and Pourdeyhimi, B.}, year={2012}, month={Sep}, pages={344–355} }
 @article{arambakam_tafreshi_pourdeyhimi_2012, title={Analytical Monte Carlo Ray Tracing simulation of radiative heat transfer through bimodal fibrous insulations with translucent fibers}, volume={55}, ISSN={0017-9310}, url={http://dx.doi.org/10.1016/j.ijheatmasstransfer.2012.07.049}, DOI={10.1016/j.ijheatmasstransfer.2012.07.049}, abstractNote={Abstract In this study, a Monte Carlo Ray Tracing (MCRT) simulation technique is developed to study steady-state radiative heat transfer through fibrous insulation materials. The simulations are conducted in 3-D disordered virtual fibrous media with unimodal and/or bimodal fiber diameter distributions consisting of fibers whose surfaces are specularly reflective, and are translucent to Infrared (IR) radiation. Scattering within the realm of geometric optics is incorporated into our MCRT simulations using Snell’s Law for ray refraction. Fibers’ optical properties are obtained from Fresnel’s law and Beer’s law based on the refractive index of the material. Two different treatments of “high” and “low” conductivities are considered for the fibers and their effects are discussed. Our results indicate that heat flux through a fibrous medium with translucent fibers decreases with increasing packing fraction of the fibers. It was observed that IR transmittance through the media increases with increasing through-plane orientation of the fibers, but is independent of their in-plane orientations. It was also found that fiber orientation has generally a negligible effect on the temperature profile across the media’s thickness. However, for the case of high-conductivity fibers, increasing fibers’ through-plane orientation tends to flatten the temperature profile. The results obtained from simulating bimodal fibrous structures indicate that increasing the fiber-diameter dissimilarity, or the mass fraction of the coarse fibers, slightly increases the radiation transmittance through the media, and accordingly reduces the temperature gradient across the thickness. Our simulation results are compared with those from the two-flux model and good agreement is observed.}, number={23-24}, journal={International Journal of Heat and Mass Transfer}, publisher={Elsevier BV}, author={Arambakam, R. and Tafreshi, H.V. and Pourdeyhimi, B.}, year={2012}, month={Nov}, pages={7234–7246} }
 @article{barth_samaha_tafreshi_gad-el-hak_2012, title={Convective Air Mass Transfer in Submerged Superhydrophobic Surfaces}, volume={57}, ISSN={0003-0503}, number={17}, journal={Bulletin of the American Physical Society}, author={Barth, C.A. and Samaha, M.A. and Tafreshi, H.V. and Gad-el-Hak, M.}, year={2012}, pages={305} }
 @article{emami_tafreshi_gad-el-hak_tepper_2012, title={Effect of fiber orientation on shape and stability of air–water interface on submerged superhydrophobic electrospun thin coatings}, volume={111}, ISSN={0021-8979 1089-7550}, url={http://dx.doi.org/10.1063/1.3697895}, DOI={10.1063/1.3697895}, abstractNote={To better understand the role of fiber orientation on the stability of superhydrophobic electrospun coatings under hydrostatic pressures, an integro-differential equation is developed from the balance of forces across the air–water interface between the fibers. This equation is solved numerically for a series of superhydrophobic electrospun coatings comprised of random and orthogonal fiber orientations to obtain the exact 3D shape of the air–water interface as a function of hydrostatic pressure. More important, this information is used to predict the pressure at which the coatings start to transition from the Cassie state to the Wenzel state, i.e., the so-called critical transition pressure. Our results indicate that coatings composed of orthogonal fibers can withstand higher elevated hydrostatic pressures than those made up of randomly orientated fibers. Our results also prove that thin superhydrophobic coatings can better resist the elevated pressures. The modeling methodology presented here can be used to design nanofibrous superhydrophobic coatings for underwater applications.}, number={6}, journal={Journal of Applied Physics}, publisher={AIP Publishing}, author={Emami, B. and Tafreshi, H. Vahedi and Gad-el-Hak, M. and Tepper, G. C.}, year={2012}, month={Mar}, pages={064325} }
 @article{gad-el-hak_samaha_tafreshi_2012, title={Effects of Hydrostatic Pressure on the Drag Reduction of Submerged Aerogel-Particle Coatings}, volume={57}, ISSN={0003-0503}, number={17}, journal={Bulletin of the American Physical Society}, author={Gad-el-Hak, M. and Samaha, M.A. and Tafreshi, H.V.}, year={2012}, pages={373} }
 @article{ochanda_samaha_tafreshi_tepper_gad-el-hak_2012, title={Effects of Salinity on Drag Reduction and Longevity of Superhydrophobic Fiber Coatings}, volume={123}, ISSN={0021-8995}, journal={Journal of Applied Polymer Science}, author={Ochanda, F. and Samaha, M.A. and Tafreshi, H.V. and Tepper, G.C. and Gad-el-Hak, M.}, year={2012}, pages={1112} }
 @article{samaha_vahedi tafreshi_gad-el-hak_2012, title={Effects of hydrostatic pressure on the drag reduction of submerged aerogel-particle coatings}, volume={399}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84859971534&partnerID=MN8TOARS}, DOI={10.1016/j.colsurfa.2012.02.025}, abstractNote={There are several techniques to fabricate superhydrophobic surfaces. The one used in this paper is closer to natural surfaces found, for example, on lotus leaves. Herein, hydrophobic aerogel particles with different average diameters are randomly deposited onto metallic substrates with a thin adhesive coating to achieve a combination of hydrophobicity and surface roughness. The resulting surfaces show different degrees of superhydrophobicity and are used to study the effects of elevated pressure on the drag reduction and the degree of hydrophobicity (survivability) of such surfaces when used for underwater applications. Several previous studies presented numerical and/or analytical models to evaluate the influence of pressure on the superhydrophobicity. Experimental studies, however, are lacking. In this work, we measure the impact of pressure on the stability of the meniscus (air–water interface). The experiments utilize three instruments: (i) a previously developed optical technique to characterize the time-dependent hydrophobicity in conjunction with a pressure vessel in which the submerged coating is exposed to elevated pressures; (ii) a parallel-plate rheometer where the coating's slip length and drag reduction are measured; and (iii) a goniometer to measure the static contact angle as well as contact-angle hysteresis. We also developed an image-thresholding technique to estimate the gas area fraction of the coating. The results indicate that there exists a new parameter, the terminal pressure, beyond which the surface undergoes a global transition from the Cassie state to the Wenzel state, and therefore can no longer generate drag reduction. This terminal pressure differs from the previously identified critical pressure. The latter is the pressure above which the surface starts the transition process at some location, but not necessarily at other spots due to the heterogeneity of the surface. For the particle coatings used herein, the terminal pressures are measured to range from 100 to 600 kPa, indicating that such coatings could potentially be used for deep underwater applications.}, journal={Colloids and Surfaces A: Physicochemical and Engineering Aspects}, author={Samaha, M.A. and Vahedi Tafreshi, H. and Gad-el-Hak, M.}, year={2012}, pages={62–70} }
 @article{samaha_tafreshi_gad-el-hak_2012, title={Influence of Flow on Longevity of Superhydrophobic Coatings}, volume={28}, ISSN={0743-7463 1520-5827}, url={http://dx.doi.org/10.1021/la301299e}, DOI={10.1021/la301299e}, abstractNote={Previous studies have demonstrated the capability of superhydrophobic surfaces to produce slip flow and drag reduction, which properties hold considerable promise for a broad range of applications. However, in order to implement such surfaces for practical utilizations, environmental factors such as water movement over the surface must be observed and understood. In this work, experiments were carried out to present a proof-of-concept study on the impact of flow on longevity of polystyrene fibrous coatings. The time-dependent hydrophobicity of a submerged coating in a pressure vessel was determined while exposing the coating to a rudimentary wall-jet flow. Rheological studies were also performed to determine the effect of the flow on drag reduction. The results show that the longevity of the surface deteriorates by increasing the flow rate. The flow appears to enhance the dissolution of air into water, which leads to a loss of drag reduction.}, number={25}, journal={Langmuir}, publisher={American Chemical Society (ACS)}, author={Samaha, Mohamed A. and Tafreshi, Hooman Vahedi and Gad-el-Hak, Mohamed}, year={2012}, month={Jun}, pages={9759–9766} }
 @inproceedings{hosseini_tafreshi_2012, title={Microscale 2-D Modeling of Instantaneous Dust Loading of Fibrous Filters}, author={Hosseini, S.A. and Tafreshi, H.V.}, year={2012}, month={Jun} }
 @inproceedings{fotovati_tafreshi_pourdeyhimi_2012, title={Modeling Dust-Loading in Pleated Depth Filters}, author={Fotovati, S. and Tafreshi, H.V. and Pourdeyhimi, B.}, year={2012}, month={Jun} }
 @inbook{tafreshi_2012, place={Boca Raton, Florida}, title={Modeling Fluid Absorption in Anisotropic Fibrous Porous Media}, ISBN={9780429105067}, url={http://dx.doi.org/10.1201/b12972-10}, DOI={10.1201/b12972-10}, booktitle={Wicking in Porous Materials: Traditional and Modern Modeling Approaches}, publisher={CRC Press}, author={Tafreshi, H.V.}, editor={Masoodi, R. and Pillai, K.M.Editors}, year={2012}, month={Oct}, pages={144–173} }
 @inproceedings{bucher_emami_tafreshi_2012, title={Modeling Superhydrophobic Surfaces Comprised of Randomly Deposited Fibers or Particles}, author={Bucher, T.M. and Emami, B. and Tafreshi, H.V.}, year={2012}, month={May} }
 @inproceedings{tafreshi_bucher_2012, title={Modeling Transport Phenomena in Anisotropic Fibrous Media}, author={Tafreshi, H.V. and Bucher, T.M.}, year={2012}, month={May} }
 @article{hosseini_vahedi tafreshi_2012, title={Modeling particle-loaded single fiber efficiency and fiber drag using ANSYS-Fluent CFD code}, volume={66}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84863844861&partnerID=MN8TOARS}, DOI={10.1016/j.compfluid.2012.06.017}, abstractNote={In this paper, we present a methodology for simulating pressure drop and collection efficiency of a filter medium during instantaneous particle loading using the ANSYS–Fluent CFD code, enhanced with in-house subroutines. The simulations are comprised of a numerical solution of the Stokes equations for obtaining the air flow field, and Lagrangian particle tracking, for determining the particle collection efficiency and particle deposition sites on the fibers. The modeling strategy presented in this work allows one to track particles of different sizes and simulate the formation of 3-D dendrite particle deposits in the presence of aerodynamic slip on the fiber surface. In particular, the deposition of particles on a fiber, and on previously deposited particles, is made possible by developing in-house subroutines, which mark the cells located at the deposition sites and modify their properties so that they resemble solid particles. Fiber drag and single fiber collection efficiencies are obtained from simulations for fibers and particles of different diameters for demonstration purposes. Effects of particle capture mechanisms on a filter’s pressure drop and collection efficiency are presented and discussed with respect to the studies reported in the literature. More specifically, two fiber diameters of 1 and 20 μm are used to demonstrate that the normalized single fiber collection efficiency increases with increasing mass of the loaded particles on the fibers (i.e., time) if the particle capture mechanism is interception or diffusion, but stays almost invariant if the capture mechanism is inertial impaction. Fiber drag (resembling the filter’s pressure drop) seems to increase because of particle deposition, but at different rates for different particle capture mechanisms.}, journal={Computers and Fluids}, author={Hosseini, S.A. and Vahedi Tafreshi, H.}, year={2012}, pages={157–166} }
 @article{bucher_emami_tafreshi_gad-el-hak_tepper_2012, title={Modeling resistance of nanofibrous superhydrophobic coatings to hydrostatic pressures: The role of microstructure}, volume={24}, ISSN={1070-6631 1089-7666}, url={http://dx.doi.org/10.1063/1.3686833}, DOI={10.1063/1.3686833}, abstractNote={In this paper, we present a numerical study devised to investigate the influence of microstructural parameters on the performance of fibrous superhydrophobic coatings manufactured via dc and ac electrospinning. In particular, our study is focused on predicting the resistance of such coatings against elevated hydrostatic pressures, which is of crucial importance for submersible applications. In our study, we generate 3D virtual geometries composed of randomly or orthogonally oriented horizontal fibers with bimodal diameter distributions resembling the microstructure of our electrospun coatings. These virtual geometries are then used as the computational domain for performing full morphology numerical simulations to establish a relationship between the coatings’ critical pressure (pressure beyond which the surface may depart from the Cassie state) and their microstructures. For coatings with ordered microstructures, we have also derived analytical expressions for the critical pressure based on the balance of forces acting on the water–air interface. Predictions of our force balance analysis are compared with those of our FM simulations as well as the equations proposed by Tuteja et al. [Proc. Natl. Acad. Sci. U.S.A. 105, 18200 (2008)]10.1073/pnas.0804872105, and discussed in detail. Our numerical simulations are aimed at providing useful information with regards to the tolerance of fibrous superhydrophobic coatings against elevated pressures, and helping with the design and optimization of the coatings’ microstructures. Our results show considerably higher pressure tolerance for the case of coatings with orthogonally oriented fibers as compared to those with randomly laid fibers when other microstructural parameters are held constant. Moreover, it is demonstrated that thickness of the coating has less influence on performance in the case of orthogonal microstructures. Coatings’ responses to other variations favor those that yield smaller-sized inter-fiber spaces. Studies are also performed investigating the effect of subtle permutations in the layer configurations of our ac-electrospun coatings, as well as the use of a hybrid coating that utilizes advantages from both dc and ac electrospinning.}, number={2}, journal={Physics of Fluids}, publisher={AIP Publishing}, author={Bucher, T. M. and Emami, B. and Tafreshi, H. Vahedi and Gad-el-Hak, M. and Tepper, G. C.}, year={2012}, month={Feb}, pages={022109} }
 @article{tepper_samaha_tafreshi_gad-el-hak_2012, title={Novel Method to Characterize Superhydrophobic Coatings}, volume={57}, ISSN={0003-0503}, number={17}, journal={Bulletin of the American Physical Society}, author={Tepper, G.C. and Samaha, M.A. and Tafreshi, H.V. and Gad-el-Hak, M.}, year={2012}, pages={100} }
 @article{emami_tafreshi_2012, title={Optimizing fiber cross-sectional shape for improving stability of air–water interface over superhydrophobic fibrous coatings}, volume={100}, ISSN={0003-6951 1077-3118}, url={http://dx.doi.org/10.1063/1.4711800}, DOI={10.1063/1.4711800}, abstractNote={In this letter, a mathematical force-balance formulation is developed that can be used to predict the critical pressure, the hydrostatic pressure above which the surface starts to depart from the non-wetting state, for superhydrophobic surfaces comprised of highly aligned fibers (e.g., biased AC-electrospun coatings) with arbitrary cross-sectional shapes. We have also developed a methodology for optimizing the fiber cross-sections to maximize the critical pressure of the surface, using the Euler–Lagrange equation. A case study is presented to better demonstrate the application of our method.}, number={19}, journal={Applied Physics Letters}, publisher={AIP Publishing}, author={Emami, B. and Tafreshi, H. Vahedi}, year={2012}, month={May}, pages={193104} }
 @article{emami_vahedi tafreshi_gad-el-hak_tepper_2012, title={Predicting shape and stability of air-water interface on superhydrophobic surfaces comprised of pores with arbitrary shapes and depths}, volume={100}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84855555035&partnerID=MN8TOARS}, DOI={10.1063/1.3673619}, abstractNote={An integro-differential equation for the three dimensional shape of air–water interface on superhydrophobic surfaces comprised of pores with arbitrary shapes and depths is developed and used to predict the static critical pressure under which such surfaces depart from the non-wetting state. Our equation balances the capillary forces with the pressure of the air entrapped in the pores and that of the water over the interface. Stability of shallow and deep circular, elliptical, and polygonal pores is compared with one another and a general conclusion is drawn for designing pore shapes for superhydrophobic surfaces with maximum stability.}, number={1}, journal={Applied Physics Letters}, author={Emami, B. and Vahedi Tafreshi, H. and Gad-El-Hak, M. and Tepper, G.C.}, year={2012} }
 @article{salinity effects on the degree of hydrophobicity and longevity for superhydrophobic fibrous coatings_2012, url={https://publons.com/wos-op/publon/42898617/}, DOI={10.1002/APP.35615}, abstractNote={Abstract}, journal={Journal of Applied Polymer Science}, year={2012} }
 @article{samaha_tafreshi_gad-el-hak_2012, title={Superhydrophobic surfaces: From the lotus leaf to the submarine}, volume={340}, ISSN={1631-0721}, url={http://dx.doi.org/10.1016/j.crme.2011.11.002}, DOI={10.1016/j.crme.2011.11.002}, abstractNote={In this review we discuss the current state of the art in evaluating the fabrication and performance of biomimetic superhydrophobic materials and their applications in engineering sciences. Superhydrophobicity, often referred to as the lotus effect, could be utilized to design surfaces with minimal skin-friction drag for applications such as self-cleaning and energy conservation. We start by discussing the concept of the lotus effect and continue to present a review of the recent advances in manufacturing superhydrophobic surfaces with ordered and disordered microstructures. We then present a discussion on the resistance of the air–water interface to elevated pressures—the phenomenon that enables a water strider to walk on water. We conclude the article by presenting a brief overview of the latest advancements in studying the longevity of submerged superhydrophobic surfaces for underwater applications.}, number={1-2}, journal={Comptes Rendus Mécanique}, publisher={Elsevier BV}, author={Samaha, Mohamed A. and Tafreshi, Hooman Vahedi and Gad-el-Hak, Mohamed}, year={2012}, month={Jan}, pages={18–34} }
 @article{tafreshi_samaha_gad-el-hak_2012, title={Sustainability of Superhydrophobicity Under Pressure}, volume={57}, ISSN={0003-0503}, number={17}, journal={Bulletin of the American Physical Society}, author={Tafreshi, H.V. and Samaha, M.A. and Gad-el-Hak, M.}, year={2012}, pages={373} }
 @article{samaha_vahedi tafreshi_gad-el-hak_2012, title={Sustainability of superhydrophobicity under pressure}, volume={24}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84872420116&partnerID=MN8TOARS}, DOI={10.1063/1.4766200}, abstractNote={Prior studies have demonstrated that superhydrophobicity of submerged surfaces is influenced by hydrostatic pressure and other environmental effects. Sustainability of a superhydrophobic surface could be characterized by both how long it maintains the trapped air in its surface pores, so-called “longevity,” and the pressure beyond which it undergoes a global wetting transition, so-called “terminal pressure.” In this work, we investigate the effects of pressure on the performance of electrospun polystyrene fibrous coatings. The time-dependent hydrophobicity of the submerged coating in a pressure vessel is optically measured under elevated pressures. Rheological studies are also performed to determine the effects of pressure on drag reduction and slip length. The measurements indicate that surface longevity exponentially decays with increasing pressure in perfect agreement with the studies reported in the literature at lower pressures. It is found, however, that fibrous coatings could resist hydrostatic pressures significantly higher than those of previously reported surfaces. Our observations indicate that superhydrophobic fibrous coatings could potentially be used for underwater applications.}, number={11}, journal={Physics of Fluids}, author={Samaha, M.A. and Vahedi Tafreshi, H. and Gad-el-Hak, M.}, year={2012} }
 @article{arambakam_hosseini_tafreshi_pourdeyhimi_2011, title={A Monte Carlo simulation of radiative heat through fibrous media: Effects of boundary conditions and microstructural parameters}, volume={50}, ISSN={1290-0729}, url={http://dx.doi.org/10.1016/j.ijthermalsci.2011.01.015}, DOI={10.1016/j.ijthermalsci.2011.01.015}, abstractNote={This work reports on a Monte Carlo Ray Tracing (MCRT) simulation technique devised to study steady-state radiative heat transfer in fibrous insulation materials. The media consist of specular opaque fibers having unimodal/bimodal fiber diameter distributions. The simulations are conducted in 2-D ordered geometries, and the role of lateral symmetric or periodic boundary conditions are discussed in detail. Our results indicate that with the symmetric or periodic boundary condition, view factor Fi,i should be excluded from the calculations leading to temperature prediction. This is especially important when the media are made of fibers arranged in ordered configurations. In agreement with our previous 3-D MCRT simulations, the 2-D MCRT simulations presented here reveal that heat flux through a fibrous medium decreases by increasing packing fraction of the fibers, when fiber diameter is kept constant. Moreover, increasing fibers’ absorptivity was found to decrease the radiation transmittance through the media. In this work, we have also studied radiative heat transfer through bimodal fibrous media, and concluded that increasing fibers’ dissimilarity increases energy transmittance through the media, if porosity and number of fibers are kept constant. It was also found that temperature of the fibers is almost independent of the media’s porosity or diameter ratios.}, number={6}, journal={International Journal of Thermal Sciences}, publisher={Elsevier BV}, author={Arambakam, R. and Hosseini, S.A. and Tafreshi, H. Vahedi and Pourdeyhimi, B.}, year={2011}, month={Jun}, pages={935–941} }
 @article{mital_tafreshi_2011, title={A methodology for determining optimal thermal damage in magnetic nanoparticle hyperthermia cancer treatment}, volume={28}, ISSN={2040-7939}, url={http://dx.doi.org/10.1002/cnm.1456}, DOI={10.1002/cnm.1456}, abstractNote={SUMMARY}, number={2}, journal={International Journal for Numerical Methods in Biomedical Engineering}, publisher={Wiley}, author={Mital, Manu and Tafreshi, Hooman V.}, year={2011}, month={Jul}, pages={205–213} }
 @inproceedings{tafreshi_pourdeyhimi_2011, title={An Overview on Micro- and Macro-Scale Modeling of Aerosol Filters}, author={Tafreshi, H.V. and Pourdeyhimi, B.}, year={2011}, month={Sep} }
 @inproceedings{bucher_tafreshi_2011, title={An Overview on Modeling Fluid Absorption in Fibrous Media}, author={Bucher, T.M. and Tafreshi, H.V.}, year={2011}, month={Sep} }
 @article{fotovati_tafreshi_pourdeyhimi_2011, title={Analytical expressions for predicting performance of aerosol filtration media made up of trilobal fibers}, volume={186}, ISSN={0304-3894}, url={http://dx.doi.org/10.1016/j.jhazmat.2010.12.027}, DOI={10.1016/j.jhazmat.2010.12.027}, abstractNote={Despite the widespread use of fibrous filtration media made up of trilobal fibers (referred to as trilobal media here), no mathematical formulations have yet been developed to predict their collection efficiency or pressure drop. In this study, we model the cross-section of a trilobal fiber with three overlapping ellipses separated from one another by a 120° transformation. We generate 2-D models representing the internal structure of trilobal filters having fibers with different dimensions and aspect ratios, and used them to predict pressure drop and collection efficiency of trilobal filter media. This information is then utilized to define an equivalent medium with circular fibers for each trilobal filter. Our results indicate that the circumscribed circle of a trilobal fiber can serve as an equivalent circular diameter, and therefore be used in the existing empirical/semi-empirical correlations that have previously been developed for predicting performance of filters with circular fibers. We have also proposed easy-to-use expressions that can be used with our equivalent circumscribed diameters for calculating the pressure drop of trilobal media.}, number={2-3}, journal={Journal of Hazardous Materials}, publisher={Elsevier BV}, author={Fotovati, S. and Tafreshi, H. Vahedi and Pourdeyhimi, B.}, year={2011}, month={Feb}, pages={1503–1512} }
 @article{gad-el-hak_.ochanda_samaha_tafreshi_tepper_2011, title={Fabrication of Superhydrophobic Fiber Coatings by DC-Biased AC-Electrospinning}, volume={56}, number={18}, journal={Bulletin of the American Physical Society}, author={Gad-el-Hak, M. and .Ochanda, F.O. and Samaha, M.A. and Tafreshi, H.V. and Tepper, G.C.}, year={2011}, pages={50} }
 @article{ochanda_samaha_tafreshi_tepper_gad-el-hak_2011, title={Fabrication of superhydrophobic fiber coatings by DC-biased AC-electrospinning}, volume={123}, ISSN={0021-8995}, url={http://dx.doi.org/10.1002/app.34583}, DOI={10.1002/app.34583}, abstractNote={Abstract}, number={2}, journal={Journal of Applied Polymer Science}, publisher={Wiley}, author={Ochanda, Fredrick O. and Samaha, Mohamed A. and Tafreshi, Hooman Vahedi and Tepper, Gary C. and Gad-el-Hak, Mohamed}, year={2011}, month={Aug}, pages={1112–1119} }
 @article{tepper_samaha_tafreshi_gad-el-hak_situ_2011, title={In Situ, Noninvasive Characterization of Superhydrophobic Coatings}, volume={56}, number={18}, journal={Bulletin of the American Physical Society}, author={Tepper, G.C. and Samaha, M.A. and Tafreshi, H.V. and Gad-el-Hak, M. and Situ, In}, year={2011}, pages={314} }
 @article{samaha_ochanda_tafreshi_tepper_gad-el-hak_2011, title={In situ</i>, noninvasive characterization of superhydrophobic coatings}, volume={82}, ISSN={0034-6748 1089-7623}, url={http://dx.doi.org/10.1063/1.3579498}, DOI={10.1063/1.3579498}, abstractNote={Light scattering was used to measure the time-dependent loss of air entrapped within a submerged microporous hydrophobic surface subjected to different environmental conditions. The loss of trapped air resulted in a measurable decrease in surface reflectivity and the kinetics of the process was determined in real time and compared to surface properties, such as porosity and morphology. The light-scattering results were compared with measurements of skin-friction drag, static contact angle, and contact-angle hysteresis. The in situ, noninvasive optical technique was shown to correlate well with the more conventional methods for quantifying surface hydrophobicity, such as flow slip and contact angle.}, number={4}, journal={Review of Scientific Instruments}, publisher={AIP Publishing}, author={Samaha, Mohamed A. and Ochanda, Fredrick O. and Tafreshi, Hooman Vahedi and Tepper, Gary C. and Gad-el-Hak, Mohamed}, year={2011}, month={Apr}, pages={045109} }
 @article{samaha_tafreshi_gad-el-hak_2011, title={Modeling Superhydrophobic Surfaces Comprised of Random Roughness}, volume={56}, number={18}, journal={Bulletin of the American Physical Society}, author={Samaha, M.A> and Tafreshi, H.V. and Gad-el-Hak, M.}, year={2011}, pages={314} }
 @article{samaha_vahedi tafreshi_gad-el-hak_2011, title={Modeling drag reduction and meniscus stability of superhydrophobic surfaces comprised of random roughness}, volume={23}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-79551512121&partnerID=MN8TOARS}, DOI={10.1063/1.3537833}, abstractNote={Previous studies dedicated to modeling drag reduction and stability of the air-water interface on superhydrophobic surfaces were conducted for microfabricated coatings produced by placing hydrophobic microposts/microridges arranged on a flat surface in aligned or staggered configurations. In this paper, we model the performance of superhydrophobic surfaces comprised of randomly distributed roughness (e.g., particles or microposts) that resembles natural superhydrophobic surfaces, or those produced via random deposition of hydrophobic particles. Such fabrication method is far less expensive than microfabrication, making the technology more practical for large submerged bodies such as submarines and ships. The present numerical simulations are aimed at improving our understanding of the drag reduction effect and the stability of the air-water interface in terms of the microstructure parameters. For comparison and validation, we have also simulated the flow over superhydrophobic surfaces made up of aligned or staggered microposts for channel flows as well as streamwise or spanwise ridges configurations for pipe flows. The present results are compared with theoretical and experimental studies reported in the literature. In particular, our simulation results are compared with work of Sbragaglia and Prosperetti, and good agreement has been observed for gas fractions up to about 0.9. The numerical simulations indicate that the random distribution of surface roughness has a favorable effect on drag reduction, as long as the gas fraction is kept the same. This effect peaks at about 30% as the gas fraction increases to 0.98. The stability of the meniscus, however, is strongly influenced by the average spacing between the roughness peaks, which needs to be carefully examined before a surface can be recommended for fabrication. It was found that at a given maximum allowable pressure, surfaces with random post distribution produce less drag reduction than those made up of staggered posts.}, number={1}, journal={Physics of Fluids}, author={Samaha, M.A. and Vahedi Tafreshi, H. and Gad-el-Hak, M.}, year={2011} }
 @article{fotovati_hosseini_tafreshi_pourdeyhimi_2011, title={Modeling instantaneous pressure drop of pleated thin filter media during dust loading}, volume={66}, ISSN={["1873-4405"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-79960251378&partnerID=MN8TOARS}, DOI={10.1016/j.ces.2011.05.038}, abstractNote={In this paper, we present a modeling methodology for studying the effects of dust loading on the pressure drop across pleated filters. Our simulations demonstrate that there exists an optimum pleat count for clean filters at which pressure drop reaches a minimum regardless of the in-plane or through-plane orientation of the fibers. With the particle deposition included in the analysis, our results indicated that the rate of increase in pressure drop decreases with increase in the pleat count. We demonstrated that a higher pleat count results in a higher flow velocity inside the pleat channels causing more non-uniformity in the dust deposition across the pleat. Especially when particles are sufficiently large, the dust cake tends to form deeper inside the pleated channel when the pleat count is high. This effect is observed to be less pronounced when the pleats have a triangular shape. We also showed that if the dust cake permeability is higher than that of the filters fibrous media, the rate of increase in pressure drop does not always decrease with increase in the pleat count. Finally, by comparing filters having 15 pleats per inch, we observed that rectangular pleats are preferred over the triangular pleats when the particles are highly inertial, i.e., filtering high-speed large particles. When particle's inertia is small, our results indicate that triangular pleats cause less pressure drop, and so are recommended.}, number={18}, journal={CHEMICAL ENGINEERING SCIENCE}, author={Fotovati, S. and Hosseini, S. A. and Tafreshi, H. Vahedi and Pourdeyhimi, B.}, year={2011}, month={Sep}, pages={4036–4046} }
 @article{ashari_bucher_tafreshi_2011, title={Modeling motion-induced fluid release from partially saturated fibrous media onto surfaces with different hydrophilicity}, volume={32}, ISSN={0142-727X}, url={http://dx.doi.org/10.1016/j.ijheatfluidflow.2011.06.002}, DOI={10.1016/j.ijheatfluidflow.2011.06.002}, abstractNote={Modeling the rate of fluid release from moving partially saturated nonwoven sheets in contact with a solid surface is a challenge, as the release rate depends on many parameters, some of which are difficult to quantify. In this paper, we report on a diffusion-controlled boundary treatment which we have developed to simulate fluid release from partially saturated porous materials onto surfaces with different hydrophilicy. The new boundary treatment considers the solid impermeable surface as a fictitious porous layer with a known fluid diffusive coefficient. Motion of the porous sheet on the surface is incorporated in the simulations by periodically resetting the saturation of the fictitious layer equal to zero, with a period obtained from the sheet’s speed of motion. Fluid transport inside the fibrous sheets is calculated by solving Richards’ equation of two-phase flows in porous media. Our numerical simulations are accompanied with experimental data obtained using a custom-made test rig for the release of liquid from partially saturated media at different speeds. It is demonstrated that the novel mathematical formulations presented here can correctly predict the rate of fluid release from moving fibrous sheets onto solid surfaces with different hydrophilicity as a function of time.}, number={5}, journal={International Journal of Heat and Fluid Flow}, publisher={Elsevier BV}, author={Ashari, A. and Bucher, T.M. and Tafreshi, H. Vahedi}, year={2011}, month={Oct}, pages={1076–1081} }
 @inproceedings{hosseini_tafreshi_2011, title={On the Drag Force and Collection Efficiency of Circular and Non-Circular, Clean and Loaded Submicron Fibers}, author={Hosseini, S.A. and Tafreshi, H.V.}, year={2011}, month={May} }
 @article{bucher_emami_tafreshi_gad-el-hak_tepper_2011, title={On the Resistance of Nanofibrous Superhydrophobic Coatings to Hydrostatic Pressures}, volume={56}, number={18}, journal={Bulletin of the American Physical Society}, author={Bucher, T.M. and Emami, B. and Tafreshi, H.V. and Gad-el-Hak, M. and Tepper, G.C.}, year={2011}, pages={175} }
 @article{hosseini_tafreshi_2011, title={On the importance of fibers' cross-sectional shape for air filters operating in the slip flow regime}, volume={212}, ISSN={0032-5910}, url={http://dx.doi.org/10.1016/j.powtec.2011.06.025}, DOI={10.1016/j.powtec.2011.06.025}, abstractNote={In this paper, we investigate the effects of fibers' cross-sectional shape on the performance of a fibrous filter in the slip and no-slip flow regimes. The slip flow regime is expected to prevail when fiber diameter is comparable in size to the mean free path of the gas molecules (about 65 nm at normal temperatures and pressures), whereas the no-slip flow regime describes the aerodynamic condition of flow through media with large fibers. Our numerical simulations conducted for flow around single fibers with different geometries indicate that, while the collection efficiency is only weakly affected by the cross-sectional shape of nanofibers, the fiber drag (i.e., permeability of the media) can be considerably influenced by the fiber's shape. Simulating the flow field around nano- and microfibers with circular, square, trilobal, and elliptical cross-sections, it was found that the more streamlined the fiber geometry, the lower the fiber drag caused by a nanofiber relative to that generated by its micron-sized counterpart.}, number={3}, journal={Powder Technology}, publisher={Elsevier BV}, author={Hosseini, S.A. and Tafreshi, H. Vahedi}, year={2011}, month={Oct}, pages={425–431} }
 @article{emami_tafreshi_gad-el-hak_tepper_2011, title={Predicting Stability of Air-Water Interface on Superhydrophobic Surfaces}, volume={56}, number={18}, journal={Bulletin of the American Physical Society}, author={Emami, B. and Tafreshi, H.V. and Gad-el-Hak, M. and Tepper, G.C.}, year={2011}, pages={55} }
 @article{emami_tafreshi_gad-el-hak_tepper_2011, title={Predicting shape and stability of air–water interface on superhydrophobic surfaces with randomly distributed, dissimilar posts}, volume={98}, ISSN={0003-6951 1077-3118}, url={http://dx.doi.org/10.1063/1.3590268}, DOI={10.1063/1.3590268}, abstractNote={A mathematical framework developed to calculate the shape of the air–water interface and predict the stability of a microfabricated superhydrophobic surface with randomly distributed posts of dissimilar diameters and heights is presented. Using the Young–Laplace equation, a second-order partial differential equation is derived and solved numerically to obtain the shape of the interface, and to predict the critical hydrostatic pressure at which the superhydrophobicity vanishes in a submersed surface. Two examples are given for demonstration of the method’s capabilities and accuracy.}, number={20}, journal={Applied Physics Letters}, publisher={AIP Publishing}, author={Emami, B. and Tafreshi, H. Vahedi and Gad-el-Hak, M. and Tepper, G. C.}, year={2011}, month={May}, pages={203106} }
 @article{ochanda_samaha_tafreshi_tepper_gad-el-hak_2011, title={Salinity Effects on Superhydrophobic Coatings}, volume={56}, number={18}, journal={Bulletin of the American Physical Society}, author={Ochanda, F.O. and Samaha, M.A. and Tafreshi, H.V. and Tepper, G.C. and Gad-el-Hak, M.}, year={2011}, pages={314} }
 @article{emami_bucher_tafreshi_pestov_gad-el-hak_tepper_2011, title={Simulation of meniscus stability in superhydrophobic granular surfaces under hydrostatic pressures}, volume={385}, ISSN={0927-7757}, url={http://dx.doi.org/10.1016/j.colsurfa.2011.05.055}, DOI={10.1016/j.colsurfa.2011.05.055}, abstractNote={In this work, a series of numerical simulations has been devised to study the performance of granular superhydrophobic surfaces under elevated hydrostatic pressures. Using balance of forces, an analytical expression has also been developed to predict the critical pressure at which a submersed idealized granular superhydrophobic surface comprised of spherical particles, orderly packed next to one another, departs from the Cassie state. Predictions of our analytical expression have been compared with those of a series of 3-D full-morphology numerical simulations, and reasonable agreement has been observed between the two methods. Full-morphology simulations were then used, for the first time, to compute the critical pressure of superhydrophobic surfaces comprised of randomly distributed spherical particles (e.g., superhydrophobic coatings developed by depositing of hydrophobic aerogel particles), where no analytical method is applicable due to the complexity of the coatings' morphology. Results of our numerical simulations indicate that for coatings made up of mono-disperse hydrophobic particles, critical pressure increases with increasing the solid volume fraction. However, increasing particle diameter results in lower critical pressures when the coating's solid volume fraction is held constant.}, number={1-3}, journal={Colloids and Surfaces A: Physicochemical and Engineering Aspects}, publisher={Elsevier BV}, author={Emami, B. and Bucher, T.M. and Tafreshi, H. Vahedi and Pestov, D. and Gad-el-Hak, M. and Tepper, G.C.}, year={2011}, month={Jul}, pages={95–103} }
 @inproceedings{fotovati_hosseini_vahedi tafreshi_pourdeyhimi_2011, title={Transient modeling of dust-loaded pleated air filters}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84883797244&partnerID=MN8TOARS}, booktitle={American Filtration and Separations Society Annual Conference 2011 - Shape up to Green}, author={Fotovati, S. and Hosseini, S.A. and Vahedi Tafreshi, H. and Pourdeyhimi, B.}, year={2011}, pages={464–470} }
 @article{hosseini_tafreshi_2010, title={3-D simulation of particle filtration in electrospun nanofibrous filters}, volume={201}, ISSN={0032-5910}, url={http://dx.doi.org/10.1016/j.powtec.2010.03.020}, DOI={10.1016/j.powtec.2010.03.020}, abstractNote={Virtual 3-D geometries resembling the internal microstructure of electrospun fibrous materials are generated in this work to simulate the pressure drop and collection efficiency of nanofibrous media when challenged with aerosol particles in the size range of 25 to 1000 nm. In particular, we solved the air flow field in the void space between the fibers in a series of 3-D fibrous geometries with a fiber diameter in the range of 100 to 1000 nm and a Solid Volume Fraction (SVF) in the range of 2.5 to 7.5%, using the Fluent CFD code, and simulated the flow of large and fine particles through these media using Lagrangian and Eulerian methods, respectively. Particle collection due to interception and Brownian diffusion, as well as the slip effect at the surface of nanofibers, has been incorporated in the CFD calculations by developing customized C++ subroutines that run in the Fluent environment. Particle collection efficiency and pressure drop of the above fibrous media are calculated and compared with analytical/empirical results from the literature. The numerical simulations presented here are believed to be the most complete and realistic filter modeling published to date. Our simulation technique, unlike previous studies based on oversimplified 2-D geometries, does not need any empirical correction factors, and can be used to directly simulate pressure drop and efficiency of any fibrous media.}, number={2}, journal={Powder Technology}, publisher={Elsevier BV}, author={Hosseini, S.A. and Tafreshi, H. Vahedi}, year={2010}, month={Jul}, pages={153–160} }
 @article{ashari_bucher_vahedi tafreshi_2010, title={A semi-analytical model for simulating fluid transport in multi-layered fibrous sheets made up of solid and porous fibers}, volume={50}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-78449255008&partnerID=MN8TOARS}, DOI={10.1016/j.commatsci.2010.08.030}, abstractNote={Direct simulation of fluid transport in fibrous media consisting of swelling (i.e., fluid-absorbing) and non-swelling (i.e., solid) fibers is a challenge. In this work, we have developed a semi-analytical modeling approach that can be used to predict the fluid absorption and release characteristics of multi-layered composite fabrics made up of swelling and non-swelling fibrous sheets. The simulations presented here are based on a numerical solution of Richards’ equation. Two different fibrous sheets composed of non-swelling (PET) and swelling (Rayon) fibers with different Solid Volume Fractions (SVFs) and thicknesses were arbitrarily chosen in this study for demonstration purposes. The sheets’ capillary pressure and relative permeability are obtained via a combination of numerical simulations and experiment. In particular, the capillary pressure expression for non-swelling media is obtained from the analytical expressions that we previously developed via 3-D microscale simulations, while the capillary pressure for swelling media is obtained via height rise experiments. The relative permeability expressions for both swelling and non-swelling media are obtained from the analytical expressions previously developed via 3-D microscale simulations, which are also in agreement with experimental correlations from the literature. On the macroscale, simulation results are reported for fluid transport in bi-layered composite fabrics, and comparison is made between the performances of these fabrics in terms of the order in which the layers are stacked on top of one another. A higher rate of absorption was observed when the layer in contact with the fluid is that comprised of swelling fibers. A similar study was conducted for motion-induced fluid release from the composite fabrics when partially-saturated with a fluid. It was shown that less fluid release is expected when the swelling sheet is placed in contact with the surface.}, number={2}, journal={Computational Materials Science}, author={Ashari, A. and Bucher, T.M. and Vahedi Tafreshi, H.}, year={2010}, pages={378–390} }
 @article{fotovati_tafreshi_ashari_hosseini_pourdeyhimi_2010, title={Analytical expressions for predicting capture efficiency of bimodal fibrous filters}, volume={41}, ISSN={["1879-1964"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-77049092273&partnerID=MN8TOARS}, DOI={10.1016/j.jaerosci.2010.01.002}, abstractNote={In this work, a series of numerical simulations are formulated for studying the performance (collection efficiency and pressure drop) of filter media with bimodal diameter distributions. While there are numerous analytical expressions available for predicting performance of filters made up of fibers with a unimodal fiber diameter distribution, there are practically no simple relations for bimodal filters. In this paper, we report on the influence of the fiber diameter dissimilarity and the number (mass) fraction of each component on the performance of a bimodal filter. Our simulation results are utilized to establish a unimodal equivalent diameter for the bimodal media, thereby taking advantage of the existing expressions of unimodal filters for capture efficiency prediction. Our results indicate that the cube root relation of Tafreshi, Rahman, Jaganathan, Wang, and Pourdeyhimi (2009) offers the closest predictions for the range of particle diameters, coarse fiber number (mass) fractions, fiber diameter ratios, and solid volume fractions (SVF) considered in this work. Our study revealed that the figure of merit (FOM) of bimodal filters increases with increasing fiber diameter ratios for Brownian particles (dp<100 nm), and decreases when challenged with larger particles. It has also been shown that when increasing the ratio of coarse fibers to fine fibers, FOM increases for Brownian particles, and decreases for larger particles.}, number={3}, journal={JOURNAL OF AEROSOL SCIENCE}, author={Fotovati, S. and Tafreshi, H. Vahedi and Ashari, A. and Hosseini, S. A. and Pourdeyhimi, B.}, year={2010}, month={Mar}, pages={295–305} }
 @inproceedings{fotovati_vahedi tafreshi_pourdeyhimi_2010, title={Capture efficiency and pressure drop of bimodal filter media}, volume={2}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84883771850&partnerID=MN8TOARS}, booktitle={American Filtration and Separations Society Annual National Conference and Exposition 2010}, author={Fotovati, S. and Vahedi Tafreshi, H. and Pourdeyhimi, B.}, year={2010}, pages={710–718} }
 @inproceedings{fotovati_vahedi tafreshi_pourdeyhimi_2010, title={Effect of fiber orientation distribution on filter performance}, volume={2}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84883817446&partnerID=MN8TOARS}, booktitle={American Filtration and Separations Society Annual National Conference and Exposition 2010}, author={Fotovati, S. and Vahedi Tafreshi, H. and Pourdeyhimi, B.}, year={2010} }
 @article{fotovati_tafreshi_pourdeyhimi_2010, title={Influence of fiber orientation distribution on performance of aerosol filtration media}, volume={65}, ISSN={["0009-2509"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-77955432242&partnerID=MN8TOARS}, DOI={10.1016/j.ces.2010.06.032}, abstractNote={This work is conducted to better our understanding of the influence of fibers’ in-plane and through-plane orientations on pressure drop and collection efficiency of fibrous media. The Stokes flow equations are numerically solved in virtual, 3-D, fibrous geometries with varying in-plane and/or through-plane orientations. Pressure drop and aerosol collection efficiency characteristics of such media are calculated and compared with available studies from the literature. Our results indicate that pressure drop and submicron particle capture efficiency of common fibrous filters with a fiber diameter of about 10 μm are independent of the in-plane orientation of the fibers, but decrease with increasing the fibers’ through-plane orientation. More interestingly, it was found that filters with higher through-plane fiber orientations have a higher figure of merit if challenged with nanoparticles. The figure of merit of these media, however, decreases as the particle size increases, reversing the effect of fibers’ through-plane orientation. It was also shown that when the diameter of the particles is comparable to that of the fibers, collection efficiency increases with decreasing the fibers’ in-plane orientation, while the pressure drop remains almost unchanged. This indicates that decreasing the fibers’ in-plane orientation increased the figure of merit of media made of nanofibers.}, number={18}, journal={CHEMICAL ENGINEERING SCIENCE}, author={Fotovati, S. and Tafreshi, H. Vahedi and Pourdeyhimi, B.}, year={2010}, month={Sep}, pages={5285–5293} }
 @inproceedings{hosseini_tafreshi_2010, title={Modeling Filtration Efficiency of Electrospun Nanofibrous Filters}, author={Hosseini, S.A. and Tafreshi, H.V.}, year={2010}, month={Aug} }
 @inproceedings{hosseini_tafreshi_2010, title={Modeling Particle Filtration in 3-D Electrospun Nanofibrous Filters}, booktitle={American Filtration and Separation Society}, author={Hosseini, S.A. and Tafreshi, H.V.}, year={2010}, month={Mar} }
 @inproceedings{hosseini_tafreshi_2010, title={Modeling Particle Loading in Fibrous Filter Media}, booktitle={American Filtration and Separation Society}, author={Hosseini, S.A. and Tafreshi, H.V.}, year={2010}, month={Mar} }
 @inproceedings{tahir_tafreshi_pourdeyhimi_2010, title={Modeling Radiative Heat Transfer in Fibrous Insulation Media}, author={Tahir, M.A. and Tafreshi, H.V. and Pourdeyhimi, B.}, year={2010}, month={Nov} }
 @article{ashari_bucher_tafreshi_tahir_rahman_2010, title={Modeling fluid spread in thin fibrous sheets: Effects of fiber orientation}, volume={53}, ISSN={0017-9310}, url={http://dx.doi.org/10.1016/j.ijheatmasstransfer.2010.01.015}, DOI={10.1016/j.ijheatmasstransfer.2010.01.015}, abstractNote={In this paper, a dual-scale model is developed to simulate the radial spreading of liquids in thin fibrous sheets. Using 3-D microscale simulations, the required constitutive equations, capillary pressure and relative permeability, have been determined at each saturation level and used in a macroscale model developed based on the Richards' equation of two-phase flow in porous media. The dual-scale approach allowed us to include the partially-saturated region of a porous medium in calculations. Simulating different fibrous sheets with identical parameters but different in-plane fiber orientations, it is revealed that the rate of fluid spread increases with increasing the in-plane alignment of the fibers. Our simulations are discussed with respect to existing studies in the literature.}, number={9-10}, journal={International Journal of Heat and Mass Transfer}, publisher={Elsevier BV}, author={Ashari, A. and Bucher, T.M. and Tafreshi, H. Vahedi and Tahir, M.A. and Rahman, M.S.A.}, year={2010}, month={Apr}, pages={1750–1758} }
 @article{hosseini_tafreshi_2010, title={Modeling particle filtration in disordered 2-D domains: A comparison with cell models}, volume={74}, ISSN={1383-5866}, url={http://dx.doi.org/10.1016/j.seppur.2010.06.001}, DOI={10.1016/j.seppur.2010.06.001}, abstractNote={In this work, Stokes equations are numerically solved in a series of 2-D geometries comprised of randomly distributed fibers, using the Fluent CFD code. Particle collection due to interception and Brownian diffusion has been incorporated in the CFD calculations by developing two C++ subroutines that run in the Fluent environment. We have also modified the Discrete Phase Model of the Fluent code to correctly predict the effect of Brownian motion on a particle trajectory, and to obtain nanoparticle collection efficiency of a filter medium via the Lagrangian method. Our simulations are aimed at studying aerosol filtration in disordered 2-D fibrous media, and their results are compared with the predictions of existing cell-model-type (ordered 2-D models) semi-analytical correlations, as well as our previous simulation data obtained from 3-D simulations. Our results revealed that disordered 2-D fiber arrangements can be utilized to predict the performance of fibrous filters with reasonable accuracy and CPU time. Collection efficiencies obtained from our 2-D models seem to be marginally lower than those of 3-D simulations, for nanoparticles, and slightly higher, for larger particles. Pressure drop predictions of disordered 2-D media are found to be lower than that of ordered 2-D models, but higher than that of 3-D fibrous models. The latter is found to be in very good agreement with experiment. We have also studied the impact of aerodynamic slip on the collection efficiency of our filter media, and concluded that aerodynamic slip improves the collection efficiency of a filter medium, especially for larger particles.}, number={2}, journal={Separation and Purification Technology}, publisher={Elsevier BV}, author={Hosseini, S.A. and Tafreshi, H. Vahedi}, year={2010}, month={Aug}, pages={160–169} }
 @article{hosseini_tafreshi_2010, title={Modeling permeability of 3-D nanofiber media in slip flow regime}, volume={65}, ISSN={0009-2509}, url={http://dx.doi.org/10.1016/j.ces.2009.12.002}, DOI={10.1016/j.ces.2009.12.002}, abstractNote={Over the last few decades, numerous analytical and/or numerical expressions have been developed for predicting the permeability of a fibrous medium. These expressions, however, are not accurate in predicting the permeability of media made up of nanofibers. This is because the previous expressions were mostly developed for coarse fibers, where using the so-called no-slip velocity boundary condition at the fiber surface is quite justified. Removing the no-slip velocity restriction in this work, we study the effect of slip flow on the permeability of fibrous materials made up of nanofibers. This has been accomplished by generating a large series of 3-D virtual geometries that resemble the microstructure of a nanofiber (e.g., electrospun) material. Stokes flow equations are solved numerically in the void space between the nanofibers, with the slip flow boundary condition developed based on the Maxwell first order model. The influence of fiber diameter and solid volume fraction (SVF) on the media's permeability is studied, and used to establish a correction factor for the existing permeability expressions when used for nanofiber media.}, number={6}, journal={Chemical Engineering Science}, publisher={Elsevier BV}, author={Hosseini, S.A. and Tafreshi, H. Vahedi}, year={2010}, month={Mar}, pages={2249–2254} }
 @article{tahir_tafreshi_hosseini_pourdeyhimi_2010, title={Modeling the role of microstructural parameters in radiative heat transfer through disordered fibrous media}, volume={53}, ISSN={0017-9310}, url={http://dx.doi.org/10.1016/j.ijheatmasstransfer.2010.06.030}, DOI={10.1016/j.ijheatmasstransfer.2010.06.030}, abstractNote={Understanding the influence of microstructural parameters on the rate of heat transfer through a disordered fibrous medium is important for the design and development of heat insulation materials. In this work, by generating virtual 3-D geometries that resemble the internal microstructure of fibrous insulation materials, we simulated the influence of diameter, orientation, and emissivity of the fibers, as well as the media’s porosity and thickness on the radiative heat transmittance. Our simulations are based on a Monte Carlo ray tracing algorithm that we have developed for studying radiative heat flow in 3-D disordered media. The media were assumed to be made up of cylindrical opaque fibers with specular surface. The advantage of our modeling approach is that it does not require any empirical input values, and can directly be used to isolate and study the role of individual microstructural parameters of the media. The major limitation of the model is that it is accurate as long as the fibers can be considered large relative to the wavelength of the incoming rays. Our results indicate that heat flux through a fibrous medium decreases by increasing the packing fraction of the fibers when the thickness and fiber diameter are kept constant. Increasing the fibers’ absorptivity (or emissivity) was observed to decrease the radiation transmittance through the media. Our simulations also revealed that for constant porosity and thickness, the heat flux transmitted across the medium can be reduced by using finer fibers. The steady state temperature profiles across the thicknesses of media with different properties were obtained and found to be independent of the fibers’ emissivity.}, number={21-22}, journal={International Journal of Heat and Mass Transfer}, publisher={Elsevier BV}, author={Tahir, M.A. and Tafreshi, H. Vahedi and Hosseini, S.A. and Pourdeyhimi, B.}, year={2010}, month={Oct}, pages={4629–4637} }
 @article{jaganathan_tafreshi_pourdeyhimi_2009, title={A realistic modeling of fluid infiltration in thin fibrous sheets}, volume={105}, ISSN={["1089-7550"]}, DOI={10.1063/1.3141737}, abstractNote={In this paper, a modeling study is presented to simulate the fluid infiltration in fibrous media. The Richards’ equation of two-phase flow in porous media is used here to model the fluid absorption in unsaturated/partially saturated fibrous thin sheets. The required consecutive equations, relative permeability, and capillary pressure as functions of medium’s saturation are obtained via fiber-level modeling and a long-column experiment, respectively. Our relative permeability calculations are based on solving the Stokes flow equations in partially saturated three-dimensional domains obtained by imaging the sheets’ microstructures. The Richards’ equation, together with the above consecutive correlations, is solved for fibrous media inclined with different angles. Simulation results are obtained for three different cases of upward, horizontal, and downward infiltrations. We also compared our numerical results with those of our long-column experiment and observed a good agreement. Moreover, we establish empirical coefficients for the semianalytical correlations previously proposed in the literature for the case of horizontal and downward infiltrations in thin fibrous sheets.}, number={11}, journal={JOURNAL OF APPLIED PHYSICS}, author={Jaganathan, Sudhakar and Tafreshi, Hooman Vahedi and Pourdeyhimi, Behnam}, year={2009}, month={Jun} }
 @article{jaganathan_tafreshi_shim_pourdeyhimi_2009, title={A study on compression-induced morphological changes of nonwoven fibrous materials}, volume={337}, ISSN={["1873-4359"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-59349102148&partnerID=MN8TOARS}, DOI={10.1016/j.colsurfa.2008.12.019}, abstractNote={Pore size is a characteristic parameter that is often defined for fibrous materials used in industrial applications. While there exist many available studies on the pore size distribution of different fibrous materials, the influence of compression load on pore size distribution has not been studied well. Studying the behavior of fibrous materials under compression is important especially because in many applications these materials are subjected to some degree of compression during use. In this work, we present a novel image-based modeling technique to study the changes in the pore size distribution of a fibrous material exposed to compressive load. This was made possible by building a miniature compression cell, and imaging the structure of a hydroentangled fabric under varying levels of compression. The 3D images obtained with Digital Volumetric Imaging were utilized to study the pore size distribution of the material and develop an empirical correlation as a function of compressive stress for these structures. This new correlation indicates that the mean pore diameter of a nonwoven material decreases exponentially with increasing the compressive stress.}, number={1-3}, journal={COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS}, author={Jaganathan, S. and Tafreshi, H. Vahedi and Shim, E. and Pourdeyhimi, B.}, year={2009}, month={Apr}, pages={173–179} }
 @article{ashari_vahedi tafreshi_2009, title={A two-scale modeling of motion-induced fluid release from thin fibrous porous media}, volume={64}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-63249099606&partnerID=MN8TOARS}, DOI={10.1016/j.ces.2009.01.048}, abstractNote={In this work, a two-scale two-phase modeling methodology is presented for studying fluid release from saturated/unsaturated thin fibrous media when brought in contact with a moving solid surface. Our macroscale model is based on the Richards’ equation for two-phase fluid transport in porous media. The required constitutive relationships, capillary pressure and relative permeability as functions of medium's saturation, are obtained through microscale modeling. At microscales, a 3-D model based on fiber diameter, fiber orientation, and medium's solid volume fraction (SVF), is generated to resemble the internal structure of the fibrous sheets and be used in full-morphology analysis as well as microscale permeability simulation. A mass convection boundary condition is considered here to model the fluid transport at the boundary in contact with the target surface. It was shown that the mass convection coefficient, kf, plays a significant role in determining the release rate and is expected to be in the range of 10-6<kf<10-9, depending on the properties of the fluid, fibrous sheet, the target surface as well as the speed of the relative motion, and remains to be determined experimentally.}, number={9}, journal={Chemical Engineering Science}, author={Ashari, A. and Vahedi Tafreshi, H.}, year={2009}, pages={2067–2075} }
 @inproceedings{fotovati_tafreshi_pourdeyhimi_2009, title={An Analytical Expression for Predicting the Pressure Drop of Bimodal Filter Media}, booktitle={American Filtration and Separation Society}, author={Fotovati, S. and Tafreshi, H.V. and Pourdeyhimi, B.}, year={2009}, month={May} }
 @article{qashou_tafreshi_pourdeyhimi_2009, title={An Investigation of the Radiative Heat Transfer through Nonwoven Fibrous Materials}, volume={4}, ISSN={1558-9250 1558-9250}, url={http://dx.doi.org/10.1177/155892500900400103}, DOI={10.1177/155892500900400103}, abstractNote={ In this study, the surface-to-surface radiation model of the Fluent CFD code is used to investigate the response of a fibrous material to the radiative heat transfer. The unsteady state heat transfer equation is solved for the temperature and heat flux in and around the fibers that constitute a nonwoven fibrous material. For a fixed fiber diameter, it was shown that the higher the fabric's Solid Volume Fraction (SVF), the slower is the material's average temperature rise. Our simulation results also indicate that for a fixed SVF, fiber diameter has a negligible influence on the unsteady transfer of heat through the media. Of particular interest in this paper is the effect of material's thickness on the heat penetration. It is shown that the transient heat transfer exponentially decreases by increasing the material's thickness for fixed SVFs and fiber diameters. The above finding is also in agreement with our experimental study. }, number={1}, journal={Journal of Engineered Fibers and Fabrics}, publisher={SAGE Publications}, author={Qashou, Imad and Tafreshi, Hooman Vahedi and Pourdeyhimi, Behnam}, year={2009}, month={Mar}, pages={155892500900400} }
 @article{tafreshi_rahman_jaganathan_wang_pourdeyhimi_2009, title={Analytical expressions for predicting permeability of bimodal fibrous porous media}, volume={64}, ISSN={["0009-2509"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-59349120565&partnerID=MN8TOARS}, DOI={10.1016/j.ces.2008.11.013}, abstractNote={Pressure drop is one of the most important characteristics of a fibrous media. While numerous analytical, numerical, and experimental published works are available for predicting the permeability of media made up of fibers with a unimodal fiber diameter distribution (referred to as unimodal media here), there are almost no easy-to-use expressions available for media with a bimodal fiber diameter distribution (referred to as bimodal media). In the present work, the permeability of bimodal media is calculated by solving the Stokes flow governing equations in a series of 3-D virtual geometries that mimic the microstructure of fibrous materials. These simulations are designed to establish a unimodal equivalent diameter for the bimodal media thereby taking advantage of the existing expressions of unimodal materials for permeability prediction. We evaluated eight different methods of defining an equivalent diameter for bimodal media and concluded that the area-weighted average diameter of Brown and Thorpe [2001. Glass-fiber filters with bimodal fiber size distributions. Powder Technology 118, 3–9], volume-weighted resistivity model of Clague and Phillips [1997. A numerical calculation of the hydraulic permeability of three dimensional disordered fibrous media. Physics of Fluids 9 (6), 1562–1572], and the cube root relation of the current paper offer the best predictions for the entire range of mass (number) fractions, 0⩽nc⩽1, with fiber diameter ratios, 1⩽Rcf⩽5, and solidities, 5⩽α⩽15.}, number={6}, journal={CHEMICAL ENGINEERING SCIENCE}, author={Tafreshi, H. Vahedi and Rahman, M. S. A. and Jaganathan, S. and Wang, Q. and Pourdeyhimi, B.}, year={2009}, month={Mar}, pages={1154–1159} }
 @article{ashari_vahedi tafreshi_2009, title={General capillary pressure and relative permeability expressions for through-plane fluid transport in thin fibrous sheets}, volume={346}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-67650573145&partnerID=MN8TOARS}, DOI={10.1016/j.colsurfa.2009.06.001}, abstractNote={The rate of fluid transport in partially saturated porous media depends on the media's instantaneous (function of saturation) relative permeability, kr(S), and capillary pressure, Pc(S). Obtaining functional relationships for relative permeability and capillary pressure is only possible via experimentation or expensive microscale simulations, and needs to be repeated for different media having different fiber diameters, thicknesses, or porosities. In this concern, we conducted series of 3-D microscale simulations to investigate the effect of the above parameters on the relative permeability and capillary pressure of fibrous porous sheets. The results of our parameter study are utilized to develop general expressions for kr(S) and Pc(S). Our general expressions are based on the existing empirical correlations of two-phase flow in granular media, and can easily be included in macroscale fluid transport equations to predict the rate of fluid release from partially saturated fibrous sheets in a time and cost-effective manner.}, number={1-3}, journal={Colloids and Surfaces A: Physicochemical and Engineering Aspects}, author={Ashari, A. and Vahedi Tafreshi, H.}, year={2009}, pages={114–122} }
 @article{tahir_vahedi tafreshi_2009, title={Influence of fiber orientation on the transverse permeability of fibrous media}, volume={21}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-70049115925&partnerID=MN8TOARS}, DOI={10.1063/1.3211192}, abstractNote={In this work, we study the influence of in-plane and through-plane fiber orientations on a fibrous medium’s transverse permeability. Three-dimensional virtual geometries resembling the microstructure of fibrous media with different fiber orientations are developed to be utilized in permeability calculations conducted by numerically solving the Stokes equations in the void space between fibers. Results of our simulations are compared to existing experimental and analytical studies from literature and excellent agreement is observed. We, in particular, demonstrate that the transverse permeability of a fibrous medium is independent of in-plane fiber orientation but increases with increasing deviation of the fibers’ through-plane angle from zero. Our findings somewhat disagree with some of the conclusions made by Stylianopoulos et al. [Phys. Fluids 20, 123601 (2008)].}, number={8}, journal={Physics of Fluids}, author={Tahir, M.A. and Vahedi Tafreshi, H.}, year={2009} }
 @inproceedings{jaganathan_tafreshi_pourdeyhimi_2009, title={Modeling Fluid Infiltration in Fibrous Materials}, booktitle={Techtextil North America}, author={Jaganathan, S. and Tafreshi, H.V. and Pourdeyhimi, B.}, year={2009}, month={Apr} }
 @inproceedings{fotovati_tafreshi_pourdeyhimi_2009, title={Modeling Performance of Multi-Layer Composite Air Filters}, booktitle={Techtextil North America}, author={Fotovati, S. and Tafreshi, H.V. and Pourdeyhimi, B.}, year={2009}, month={Apr} }
 @inproceedings{fotovati_tafreshi_pourdeyhimi_2009, title={Modeling Pressure Drop and Collection Efficiency of Micro- and Nanofiber Filters}, booktitle={Nanofibers For The 3rd Millennium - Nano For Life}, author={Fotovati, S. and Tafreshi, H.V. and Pourdeyhimi, B.}, year={2009}, month={Mar} }
 @misc{nasr_ahmadi_tafreshi_mclaughlin_2009, title={Motion of Liquid Drops Through Complex 3D Clothing}, url={http://dx.doi.org/10.1115/fedsm2009-78283}, DOI={10.1115/fedsm2009-78283}, abstractNote={This study was concerned with the numerical simulation of a moving drop through a fabric due to a wettability gradient. The wettability gradient was introduced by varying the contact angle along the staggered fibers of a fabric. The unsteady laminar Navier-Stokes equation was solved using a fixed Eulerian unstructured grid. The Volume of Fluid Model (VOF) was used to account for tracking the gas/liquid interface. A water drop was placed on top of the fabric with an initial velocity, and the motion of the drop through the fabric was studied. Several computer simulations under different conditions such as the distance between fibers, contact angle distribution, and drop initial velocity were performed, and the results were compared with each other. In order to verify the accuracy of the computational model, the motion of a drop on a surface due to a wettabily gradient was simulated as a benchmark.}, journal={Volume 1: Symposia, Parts A, B and C}, publisher={ASMEDC}, author={Nasr, Hojjat and Ahmadi, Goodarz and Tafreshi, Homan and McLaughlin, John B.}, year={2009}, month={Jan} }
 @article{special issue: modeling foreword_2009, url={https://publons.com/wos-op/publon/65200210/}, journal={Journal of Engineered Fibers and Fabrics}, year={2009} }
 @inproceedings{hosseini_tafreshi_2009, title={Three-dimensional Simulation of Particle Filtration in Electrospun Nanofibrous Filters}, booktitle={American Filtration and Separation Society}, author={Hosseini, S.A. and Tafreshi, H.V.}, year={2009}, month={May} }
 @inproceedings{fotovati_tafreshi_pourdeyhimi_2009, title={Two-dimensional Modeling of Nanoparticle Collection Efficiency in Bimodal Filters}, booktitle={American Filtration and Separation Society}, author={Fotovati, S. and Tafreshi, H.V. and Pourdeyhimi, B.}, year={2009}, month={May} }
 @inproceedings{jaganathan_tafreshi_pourdeyhimi_2008, title={A CFD-based Two-Scale modeling approach to predict permeability of fibrous structures}, booktitle={American Filtration and Separation Society}, author={Jaganathan, S. and Tafreshi, H.V. and Pourdeyhimi, B.}, year={2008}, month={May} }
 @article{jaganathan_tafreshi_pourdeyhimi_2008, title={A Case Study of Realistic Two-Scale Modeling of Water Permeability in Fibrous Media}, volume={43}, ISSN={0149-6395 1520-5754}, url={http://dx.doi.org/10.1080/01496390802063960}, DOI={10.1080/01496390802063960}, abstractNote={Abstract There are several 3-D analytical models available for predicting the permeability of fibrous media. These models are developed based on the assumption that the medium is homogeneous with fibers oriented either in one specific direction, randomly oriented in the plane of the material, or isotropically oriented in a 3-D space. Unlike the homogeneous geometries normally considered for modeling, real media have a rather inhomogeneous Solid Volume Fraction (SVF), fiber orientations, and/or diameters. The presence of such non-uniformities in a real medium renders the models' predictions inaccurate. Sectioning-imaging, MRI imaging, or tomographic methods are often used to obtain a 3-D image of the real media for the purpose of calculating the permeability. These techniques, however, require extensive computational resources making the simulations limited to very small sub-domains. To circumvent this problem (required computational memory), a two-scale modeling approach is proposed that allowed modeling the entire thickness of a typical hydroentangled fabric on a personal computer. In particular, the micro-scale water permeability of a carded, hydroentangled nonwoven is computed via a finite difference CFD code, GeoDict, by using 3-D reconstructed microstructures obtained from Digital Volumetric Imaging (DVI). The resulting permeability tensors are then used in a lumped porous media model developed by Fluent Inc. for simulating water flow through the entire thickness of the material and the calculation of effective permeability. The modeling strategy presented in this study, is not limited to the case considered here and can be applied to different porous materials.}, number={8}, journal={Separation Science and Technology}, publisher={Informa UK Limited}, author={Jaganathan, Sudhakar and Tafreshi, Hooman Vahedi and Pourdeyhimi, Behnam}, year={2008}, month={May}, pages={1901–1916} }
 @inproceedings{jaganathan_tafreshi_pourdeyhimi_2008, title={A New Approach for Modeling Permeability of Fibrous Materials}, booktitle={International Nonwoven Technical Conference (INTC 2008)}, author={Jaganathan, S. and Tafreshi, H.V. and Pourdeyhimi, B.}, year={2008}, month={Sep} }
 @article{latifi_tafreshi_pourdeyhimi_2008, title={A Note on an Optical Method to Evaluate Fiber Dispersion in Wet-laid Nonwoven Process}, volume={78}, ISSN={0040-5175 1746-7748}, url={http://dx.doi.org/10.1177/0040517507081910}, DOI={10.1177/0040517507081910}, abstractNote={ A laboratory set-up using an online vision system was designed to observe the dispersion behavior of glass and polyester fibers. The effect of different blend ratios, agitation speed, and dispersion time in dispersing “logs” and formation of “ropes”, was studied. Our results indicate that there is a specific dispersion time period in which optimum fiber dispersion can be achieved. This time was found to be shorter for glass fibers. It was observed that the dispersion behavior of each fiber type has a profound influence on the dispersion of fiber blends. It was also noted that there is an optimum agitation energy which allows the logs to be dispersed while minimizing the rope formation. }, number={6}, journal={Textile Research Journal}, publisher={SAGE Publications}, author={Latifi, M. and Tafreshi, H. Vahedi and Pourdeyhimi, B.}, year={2008}, month={Jun}, pages={518–523} }
 @inproceedings{jaganathan_tafreshi_pourdeyhimi_2008, title={A Realistic Approach for Modeling Permeability of Fibrous Media}, booktitle={TechTextil}, author={Jaganathan, S. and Tafreshi, H.V. and Pourdeyhimi, B.}, year={2008}, month={Apr} }
 @article{jaganathan_vahedi tafreshi_pourdeyhimi_2008, title={A realistic approach for modeling permeability of fibrous media: 3-D imaging coupled with CFD simulation}, volume={63}, ISSN={0009-2509}, url={http://dx.doi.org/10.1016/j.ces.2007.09.020}, DOI={10.1016/j.ces.2007.09.020}, abstractNote={Determining permeability of fibrous media is of great importance to many industries. While there are several 2-D and 3-D analytical models developed for predicting the permeability of fibrous disordered media, there are not many numerical works that compare the predictions of these models with that of real media. In this work, we present a series of numerical simulations performed on the microstructure of a real fibrous media. An efficient procedure is presented for reconstructing 3-D images from the 2-D images of the real fibrous media and processing them for the purpose of performing fluid flow simulation. Digital volumetric imaging (DVI) of a typical hydroentangled fibrous fabric is obtained, as an example, and its permeability is computed. These results are compared with those obtained from the analytical equations given in the literature. In particular, it was found that permeability of a typical hydroentangled material can be closely predicted by the layered anisotropic models.}, number={1}, journal={Chemical Engineering Science}, publisher={Elsevier BV}, author={Jaganathan, S. and Vahedi Tafreshi, H. and Pourdeyhimi, B.}, year={2008}, month={Jan}, pages={244–252} }
 @inproceedings{jaganathan_tafreshi_pourdeyhimi_2008, title={An Image-based Approach for Modeling Permeability of Fibrous Filters}, booktitle={American Filtration and Separation Society}, author={Jaganathan, S. and Tafreshi, H.V. and Pourdeyhimi, B.}, year={2008}, month={May} }
 @article{case studies of air filtration at microscales: micro- and nanofiber media_2008, url={https://publons.com/wos-op/publon/65200208/}, journal={Journal of Engineered Fibers and Fabrics}, year={2008} }
 @article{maze_tafreshi_pourdeyhimi_2008, title={Case studies of air filtration at microscales: Micro- and nanofiber media}, volume={3}, ISBN={1558-9250}, number={2}, journal={Journal of Engineered Fibers and Fabrics}, author={Maze, B. and Tafreshi, H. V. and Pourdeyhimi, B.}, year={2008} }
 @inproceedings{wang_tafreshi_pourdeyhimi_2008, title={Modeling Permeability of Bicomponent Fibrous Filters}, booktitle={American Filtration and Separation Society}, author={Wang, Q. and Tafreshi, H.V. and Pourdeyhimi, B.}, year={2008}, month={May} }
 @article{jaganathan_vahedi tafreshi_pourdeyhimi_2008, title={Modeling liquid porosimetry in modeled and imaged 3-D fibrous microstructures}, volume={326}, ISSN={0021-9797}, url={http://dx.doi.org/10.1016/j.jcis.2008.07.011}, DOI={10.1016/j.jcis.2008.07.011}, abstractNote={In this paper, an analysis to distinguish the geometric and porosimetric pore size distributions of a fibrous material is presented. The work is based on simulating the intrusion of nonwetting fluid in a series of 3-D fibrous microstructures obtained from 3-D image reconstruction or virtual geometries mathematically generated according to the properties of the media. We start our study by computing the pore size distribution of two typical hydroentangled nonwoven materials and present a theoretical model for their geometric pore size distributions based on Poisson line network model of the fibrous media. It is shown that the probability density function of the geometric pore size distribution can be approximated by a two-parametric Gamma distribution. We also study connectivity of the pore space in fibrous media by computing and comparing the accessible and allowed pore volumes in the form access function graphs. It is shown that the so-called ink-bottle effect can significantly influence the fluid intrusion in a porous material. The pore space connectivity of a homogeneous fibrous media is observed to be a function of thickness, solid volume fraction (SVF), and fiber diameter. It is shown that increasing the materials' thickness or SVF, while other properties are kept constant, reduces the pore space connectivity. On the other hand, increasing the fiber diameter enhances the connectivity of the pores if all other parameters are fixed. Moreover, modeling layered fibrous microstructures; it is shown that the access function graphs can be used to detect the location of the bottle neck pores in a layered/composite porous material.}, number={1}, journal={Journal of Colloid and Interface Science}, publisher={Elsevier BV}, author={Jaganathan, S. and Vahedi Tafreshi, H. and Pourdeyhimi, B.}, year={2008}, month={Oct}, pages={166–175} }
 @article{jaganathan_tafreshi_pourdeyhimi_2008, title={On the pressure drop prediction of filter media composed of fibers with bimodal diameter distributions}, volume={181}, ISSN={["1873-328X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-37849049035&partnerID=MN8TOARS}, DOI={10.1016/j.powtec.2007.07.002}, abstractNote={In addition to collection efficiency, pressure drop is the most important characteristic of a filter medium. While there are numerous analytical expressions available for predicting the pressure drop of the filters made up of fibers with a unimodal fiber diameter distribution, there are not enough studies dedicated to filters composed of fibers with a bimodal (or multimodal) fiber diameter distribution. In this work, the pressure drop per unit thickness of filters made of bimodal fiber diameters is calculated by solving the Navier–Stokes equations in a series of 2-D geometries. These results are used to find the unimodal equivalent diameters of each bimodal filter that could be used in the existing expressions for calculating pressure drop. In agreement with the work of Brown and Thorpe [Brown, R.C., Thorpe, A., Glass-fiber filters with bimodal fiber size distributions. Powder Technology 118 (2001) 3–9.], it was found that the area-weighted averaging of the fiber diameters in a bimodal filter provides a relatively good estimation of its equivalent unimodal fiber diameter. We, however, noticed that in such an averaging the error percentage in the pressure drop prediction is sensitive to the fiber diameter ratios as well as the fraction of each fiber diameter in the bimodal filter. We, therefore, obtained a correction factor for the estimation of the unimodal equivalent diameters as a function of fiber diameter ratio and their number fractions.}, number={1}, journal={POWDER TECHNOLOGY}, author={Jaganathan, S. and Tafreshi, H. Vahedi and Pourdeyhimi, B.}, year={2008}, month={Jan}, pages={89–95} }
 @article{karaguzel_tafreshi_pourdeyhimi_2008, title={Potentials and challenges in jetting microdroplets onto nonwoven fabrics}, volume={99}, ISSN={["1754-2340"]}, DOI={10.1080/00405000701609282}, abstractNote={Abstract Nonwoven fabrics are very diverse in their structural properties. This paper discusses potential opportunities and challenges involved in jetting and depositing microdroplets on such materials. This study reports on the interaction of controlled droplets with the nonwoven substrates. Droplets used had velocities of about 1.8 m/s and diameters of about 90 μm and were produced by using a drop-on-demand (DOD) inkjet printhead. Nonwovens used consisted of two groups of high and low solid volume fraction (SVF) substrates. The results indicate that in the case of low-SVF nonwovens, the local spacing and orientation of the fibres plays a significant role in determining the outcomes of the jetting process. Drops were seen to penetrate deep into a low-SVF nonwoven and deposit on a single fibre or bundle of fibres. Low-SVF nonwovens, therefore, can hold the fluid within their structures—a case of interest in printing electric circuits. The case of jetting on high-SVF nonwovens was found to be primarily dependent on the fibres' surface properties. The drops were found to stay above the surface in the case of hydrophobic fibres and below the surface in the case hydrophilic ones.}, number={6}, journal={JOURNAL OF THE TEXTILE INSTITUTE}, author={Karaguzel, B. and Tafreshi, H. Vahedi and Pourdeyhimi, B.}, year={2008}, pages={581–589} }
 @article{jaganathan_maze_tafreshi_pourdeyhimi_2008, title={Simulating Liquid Flow through Virtual Glass Fiber Mats}, volume={78}, ISSN={["1746-7748"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-52949145262&partnerID=MN8TOARS}, DOI={10.1177/0040517507085195}, abstractNote={ The focus of this paper is on simulating the in-plane and through-plane penetration of liquid water in virtual non-wovens. We consider a series of unsteady state two-phase (air—water) simulations performed in two-dimensional geometries obtained from a simulated three-dimensional glass fiber mat. The simulation planes are the cross-sectional planes in the horizontal and vertical directions. Simulations revealed that liquid penetration and spread depend strongly on the fiber orientation distribution as well as on the hydrophilic properties of the fibers. Our results are in good qualitative agreement with the available experimental data. }, number={10}, journal={TEXTILE RESEARCH JOURNAL}, author={Jaganathan, S. and Maze, B. and Tafreshi, H. Vahedi and Pourdeyhimi, B.}, year={2008}, month={Oct}, pages={903–910} }
 @inproceedings{wang_tafreshi_pourdeyhimi_2008, title={Simulating Pressure Drop of Bicomponent Air Filters}, booktitle={International Nonwoven Technical Conference (INTC 2008)}, author={Wang, Q. and Tafreshi, H.V. and Pourdeyhimi, B.}, year={2008}, month={Sep} }
 @misc{pourdeyhimi_tafreshi_anantharamaiah_2008, title={System and method for reducing jet streaks in hydroentangled fibers}, volume={7,467,446}, number={2008 Dec. 23}, author={Pourdeyhimi, B. and Tafreshi, H. V. and Anantharamaiah, N.}, year={2008} }
 @article{jaganathan_tafreshi_pourdeyhimi_2008, title={The influence of forming surface on the vacuum pressure in hydroentangling process}, volume={99}, ISSN={["1754-2340"]}, DOI={10.1080/00405000701692338}, abstractNote={Hydroentangling is a process that uses waterjet curtains issued from a series of parallel jet-heads (manifolds) for entangling and interloping fibres in a loose fibre web carried on a belt or perforated surface. The efficient removal of the stagnant water remaining from each waterjet curtain is crucial for the success of fibre entanglement when the web reaches the next jet-head. In this article, we discuss different methodologies that can be used to calculate the minimum vacuum pressure required for extracting the hydroentangling water from non-woven fabrics. A distinction has been made between hydroentangling on tightly and openly woven screens and different modelling strategies are recommended for each. In particular, it is demonstrated that a one-dimensional flow pattern coupled with available analytical permeability expressions can be used to predict the required vacuum pressure in the case of tightly woven screens. In the case of open woven screens where the flow pattern becomes three-dimensional, numerical simulation is needed for calculating the vacuum pressure required for complete removal of hydroentangling water. We also demonstrated that the vacuum pressure increases by decreasing the fibre diameter or increasing the fabrics' solid volume fractions.}, number={5}, journal={JOURNAL OF THE TEXTILE INSTITUTE}, author={Jaganathan, S. and Tafreshi, H. Vahedi and Pourdeyhimi, B.}, year={2008}, pages={407–414} }
 @article{jaganathan_tafreshi_pourdeyhimi_2008, title={Two-Scale Modeling Approach to Predict Permeability of Fibrous Media}, volume={3}, ISSN={1558-9250 1558-9250}, url={http://dx.doi.org/10.1177/155892500800300208}, DOI={10.1177/155892500800300208}, abstractNote={ We previously demonstrated how one can develop a 3–D geometry to model the fibrous microstructure of a nonwoven fiberweb and use it to simulate its permeability at fiber level [1–6]. Developing 3–D models of most nonwoven fabrics (bonded fiberwebs), however, is cumbersome, as in the case of hydroentangled fabrics, for instance. In such cases, microscopic techniques are often used to generate 3–D images of the media's microstructures. Nevertheless, whether the microstructure is modeled or obtained from 3–D imaging, extensive computational resources are required to use them in fluid flow simulations [7]. To circumvent this problem, a two-scale modeling approach is proposed here that allows us to simulate the entire thickness of a commercial fabric/filter on a personal computer. In particular, the microscale permeability of a hydroentangled nonwoven is computed using 3–D reconstructed microstructures obtained from Digital Volumetric Imaging (DVI). The resulting microstructural permeability tensors are then used in a macroscale porous model to simulate the flow through the material's thickness and the calculation of its overall permeability. }, number={2}, journal={Journal of Engineered Fibers and Fabrics}, publisher={SAGE Publications}, author={Jaganathan, Sudhakar and Tafreshi, Hooman V. and Pourdeyhimi, Behnam}, year={2008}, month={Jun}, pages={155892500800300} }
 @article{pourdeyhimi_tafreshi_maze_2007, title={3-D simulation and analysis of nonwoven structures}, volume={1}, number={2}, journal={Journal of Engineered Fibers and Fabrics}, author={Pourdeyhimi, B. and Tafreshi, H. V. and Maze, B.}, year={2007}, pages={47–52} }
 @inproceedings{jaganathan_vahedi tafreshi_anantharamaiah_pourdeyhimi_2007, title={A note on water management in hydroentangling process}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-52649097032&partnerID=MN8TOARS}, booktitle={International Nonwovens Technical Conference, INTC 2007: Joint INDA-TAPPI Conference}, author={Jaganathan, S. and Vahedi Tafreshi, H. and Anantharamaiah, N. and Pourdeyhimi, B.}, year={2007}, pages={545–551} }
 @article{anantharamaiah_roempert_tafreshi_pourdeyhimi_2007, title={A novel nozzle design for producing hydroentangled nonwoven materials with minimum jet-mark defects}, volume={42}, ISSN={["1573-4803"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-34547326805&partnerID=MN8TOARS}, DOI={10.1007/s10853-006-1164-7}, number={15}, journal={JOURNAL OF MATERIALS SCIENCE}, author={Anantharamaiah, Nagendra and Roempert, Katharina and Tafreshi, Hooman Vahedi and Pourdeyhimi, Behnam}, year={2007}, month={Aug}, pages={6161–6170} }
 @article{anantharamaiah_tafreshi_pourdeyhimi_2007, title={A simple expression for predicting the inlet roundness of micro-nozzles}, volume={17}, ISSN={["1361-6439"]}, DOI={10.1088/0960-1317/17/5/N01}, abstractNote={The inlet roundness of micro-nozzles can directly influence properties of the liquid jets conducted through them. Obtaining accurate information regarding the inlet roundness of such tiny nozzles, however, is not easy. This is mainly due to the minute dimensions of these nozzles which render most nondestructive examination methods ineffective. In this study, a series of steady-state two-phase computational fluid dynamics simulations is performed to predict the inlet roundness of micro-nozzles used for producing constricted waterjets, i.e., waterjets resulting from a detached nozzle flow. Different micro-nozzles with inlet roundness ranging from r/d = 0 to 0.18 (where r and d are the inlet radius of curvature and the capillary diameter, respectively) were considered to obtain an expression for predicting the nozzle's inlet roundness as a function of its discharge coefficient. It is demonstrated that the discharge coefficient of nozzles conducting a detached flow increases with increasing inlet roundness. The inlet roundness predicted by our expression is in good agreement with the actual roundness determined by sectioning the nozzle and imaging its cross-section. Our expression is believed to be useful for manufacturers and users of capillary micro-nozzles for producing liquid micro-jets.}, number={5}, journal={JOURNAL OF MICROMECHANICS AND MICROENGINEERING}, author={Anantharamaiah, N. and Tafreshi, H. Vahedi and Pourdeyhimi, B.}, year={2007}, month={May}, pages={N31–N39} }
 @article{maze_tafreshi_wang_pourdeyhimi_2007, title={A simulation of un-steady-state filtration via nanofiber media at reduced operating pressures}, volume={38}, ISSN={["1879-1964"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-34249003346&partnerID=MN8TOARS}, DOI={10.1016/j.jaerosci.2007.03.008}, abstractNote={In this work, 3-D structures resembling nanofiber (df<200nm) filter media are simulated and challenged with nanoparticle aerosols at reduced operating pressures. For the range of fiber diameters considered in this paper, the free molecular flow regime is dominant. Therefore, the disturbances to the air flow field caused by the fibers are neglected. Nanoparticle capture efficiency of nanofiber webs, due to Brownian diffusion and interception, is calculated for particle diameters ranging from 50 to 500 nm. Our simulations show that by decreasing the fiber diameter, the minimum collection efficiency of filtration media having identical pressure drops increases. This effect is accompanied by a decrease in the particle diameter associated with these minimum efficiencies—the most penetrating particle diameter. Moreover, it is demonstrated that increasing the flow temperature enhances the nanoparticle capture efficiency of nanofiber filters. Allowing the particles to deposit on the fibers as well as each other, the caking process of such nanofiber filters is simulated for different monodisperse and polydisperse aerosols at different temperatures. The statistical information regarding the composition of nanoparticle cakes formed at high and low temperatures is presented and discussed.}, number={5}, journal={JOURNAL OF AEROSOL SCIENCE}, author={Maze, B. and Tafreshi, H. Vahedi and Wang, Q. and Pourdeyhimi, B.}, year={2007}, month={May}, pages={550–571} }
 @book{dixon_lowder_pourdeyhimi_tafreshi_2007, title={Composite Hydroentangling Nozzle Strip and Method for Producing Nonwoven Fabrics Therewith}, number={US7237308B2}, author={Dixon, D. and Lowder, J.T. and Pourdeyhimi, B. and Tafreshi, H.V.}, year={2007}, month={Jul} }
 @misc{dixon_lowder_pourdeyhimi_tafreshi_2007, title={Composite hydroentangling nozzle strip and method for producing nonwoven fabrics therewith}, volume={7,237,308}, number={2007 Jul. 3}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Dixon, M. D. and Lowder, J. T. and Pourdeyhimi, B. and Tafreshi, H. V.}, year={2007} }
 @inproceedings{jaganathan_vahedi tafreshi_pourdeyhimi_2007, title={Fluid absorption properties of nonwoven fabric: Analysis of real geometries via Digital Volumetric Imaging}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84902662663&partnerID=MN8TOARS}, booktitle={Fiber Society 2007 Spring Conference - Advanced Polymer Fiber Materials Science and its Applications in Novel Engineered Products}, author={Jaganathan, S. and Vahedi Tafreshi, H. and Pourdeyhimi, B.}, year={2007} }
 @article{maze_tafreshi_pourdeyhimi_2007, title={Geometrical modeling of fibrous materials under compression}, volume={102}, ISSN={["1089-7550"]}, DOI={10.1063/1.2794476}, abstractNote={Many fibrous materials such as nonwovens are consolidated via compaction rolls in a so-called calendering process. Hot rolls compress the fiber assembly and cause fiber-to-fiber bonding resulting in a strong yet porous structure. In this paper, we describe an algorithm for generating three dimensional virtual fiberwebs and simulating the geometrical changes that happen to the structure during the calendering process. Fibers are assumed to be continuous filaments with square cross sections lying randomly in the x or y direction. The fibers are assumed to be flexible to allow bending over one another during the compression process. Lateral displacement is not allowed during the compaction process. The algorithm also does not allow the fibers to interpenetrate or elongate and so the mass of the fibers is conserved. Bending of the fibers is modeled either by considering a constant “slope of bending” or constant “span of bending.” The influence of the bending parameters on the propagation of compression through the material’s thickness is discussed. In agreement with our experimental observations, it was found that the average solid volume fraction profile across the thickness becomes U shaped after the calendering. The application of these virtual structures in studying transport phenomena in fibrous materials is also demonstrated.}, number={7}, journal={JOURNAL OF APPLIED PHYSICS}, author={Maze, Benoit and Tafreshi, Hooman Vahedi and Pourdeyhimi, Behnam}, year={2007}, month={Oct} }
 @inproceedings{maze_vahedi tafreshi_pourdeyhimi_2007, title={Geometrical modeling of fibrous materials under compression}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-52649113309&partnerID=MN8TOARS}, booktitle={International Nonwovens Technical Conference, INTC 2007: Joint INDA-TAPPI Conference}, author={Maze, B. and Vahedi Tafreshi, H. and Pourdeyhimi, B.}, year={2007}, pages={579–587} }
 @book{pourdeyhimi_tafreshi_2007, title={Improved Long Lasting Hydroentangling Orifice Jet Strips}, number={US7303465 B2}, author={Pourdeyhimi, B. and Tafreshi, H.V.}, year={2007}, month={Dec} }
 @inproceedings{wang_maze_vahedi tafreshi_pourdeyhimi_2007, title={Modeling aerosol filtration via fibrous filter media}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84902688737&partnerID=MN8TOARS}, booktitle={Fiber Society 2007 Spring Conference - Advanced Polymer Fiber Materials Science and its Applications in Novel Engineered Products}, author={Wang, Q. and Maze, B. and Vahedi Tafreshi, H. and Pourdeyhimi, B.}, year={2007} }
 @inproceedings{wang_maze_vahedi tafreshi_pourdeyhimi_2007, title={Modeling filtration properties of staple nonwoven media}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-52649164158&partnerID=MN8TOARS}, booktitle={International Nonwovens Technical Conference, INTC 2007: Joint INDA-TAPPI Conference}, author={Wang, Q. and Maze, B. and Vahedi Tafreshi, H. and Pourdeyhimi, B.}, year={2007}, pages={654–657} }
 @article{wang_maze_tafreshi_pourdeyhimi_2007, title={On the pressure drop modeling of monofilament-woven fabrics}, volume={62}, ISSN={["1873-4405"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-34547431624&partnerID=MN8TOARS}, DOI={10.1016/j.ces.2007.06.001}, abstractNote={Pressure drop of monofilament-woven fabrics is often calculated via the so-called orifice model in which a discharge coefficient is assigned to the weave's unit cell. In all previous models of woven fabrics, the filaments were assumed to have circular cross-sections—an assumption which is not entirely accurate especially when there is a considerable tension in the warps and wefts. Following the methodology developed by Lu et al. [1996. Fluid flow through basic weaves of monofilament filter cloth. Textile Research Journal 66 (5), 311–323], a new set of expressions are derived for calculating the most constricted open area, and so the discharge coefficient, of plain-woven monofilament fabrics having filaments with elliptical cross-sections. Conducting numerical simulations for computing the pressure drop of such fabrics, we observed a logarithmic relationship between the discharge coefficient and the Reynolds number. It was also shown that the discharge coefficient decreases by increasing the aspect ratio of the filaments’ cross-section.}, number={17}, journal={CHEMICAL ENGINEERING SCIENCE}, author={Wang, Q. and Maze, B. and Tafreshi, H. Vahedi and Pourdeyhimi, B.}, year={2007}, month={Sep}, pages={4817–4821} }
 @inproceedings{jaganathan_vahedi tafreshi_pourdeyhimi_2007, title={On the pressure drop prediction of filter media composed of fibers having a bimodal fiber diameter distribution}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-52649126298&partnerID=MN8TOARS}, booktitle={International Nonwovens Technical Conference, INTC 2007: Joint INDA-TAPPI Conference}, author={Jaganathan, S. and Vahedi Tafreshi, H. and Pourdeyhimi, B.}, year={2007}, pages={658–664} }
 @inproceedings{ahmadi_tafreshi_2007, title={Overview of Flow through Textile and Fabrics}, booktitle={Marie Curie Workshop on Flow and Transport in Industrial Porous Media}, author={Ahmadi, G. and Tafreshi, H.V.}, year={2007}, month={Nov} }
 @inproceedings{wang_maze_vahedi tafreshi_pourdeyhimi_2007, title={Pressure drop simulation of multifilament woven fabrics}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84902683016&partnerID=MN8TOARS}, booktitle={Fiber Society 2007 Spring Conference - Advanced Polymer Fiber Materials Science and its Applications in Novel Engineered Products}, author={Wang, Q. and Maze, B. and Vahedi Tafreshi, H. and Pourdeyhimi, B.}, year={2007} }
 @article{zobel_maze_tafreshi_wang_pourdeyhimi_2007, title={Simulating permeability of 3-D calendered fibrous structures}, volume={62}, ISSN={["1873-4405"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-34848892122&partnerID=MN8TOARS}, DOI={10.1016/j.ces.2007.07.007}, abstractNote={Many fibrous materials such as nonwoven materials are often consolidated by means of hot calenders, i.e., hot compaction rolls. Hot calendering compresses the fiber assembly and can cause changes in the structure. In nonwovens, calendering has an added function of thermally bonding the fibers at their respective crossovers to form a strong but yet somewhat porous material. Calendering causes a significant increase in the solid volume fraction (SVF) of the media and therefore, affects their permeability. To our knowledge, no work in the literature has been dedicated to modeling the permeability of calendered nonwovens. In this study, virtual nonwoven structures are generated and compressed from top and bottom to resemble the hot calendering process. In agreement with our experimental observations, it was found that the average SVF profile across the material's thickness turns into a U-shape profile after the calendering. In this work, the dimensionless permeability of the calendered media is computed using CFD tools and reported for different compaction ratios. Results of our simulations are compared with the experiment as well as the available empirical and/or analytical permeability models in the literature and good agreement, depending upon the SVF, is observed. We also studied the influence of orientation distribution of the fibers on the dimensionless permeability of the fabric and noticed that permeability decreases by increasing the directionality of the fibers. This is found to be primarily due to the fact that highly oriented uncompressed fiber-webs tend to have a higher SVF. Fiber-webs of identical SVF, however, exhibited almost identical permeabilities regardless of their fiber orientations.}, number={22}, journal={CHEMICAL ENGINEERING SCIENCE}, author={Zobel, S. and Maze, B. and Tafreshi, H. Vahedi and Wang, Q. and Pourdeyhimi, B.}, year={2007}, month={Nov}, pages={6285–6296} }
 @article{wang_maze_tafreshi_pourdeyhimi_2007, title={Simulating through-plane permeability of fibrous materials with different fiber lengths}, volume={15}, ISSN={["0965-0393"]}, DOI={10.1088/0965-0393/15/8/003}, abstractNote={Assuming that fibers can be represented as straight cylinders, an algorithm for generating virtual 3D layered fibrous media made up of fibers having identical diameters but different lengths is presented. It is shown that for a given basis weight and computational box (sample size), reducing the fiber length causes the solid volume fraction (SVF) to increase as the fibers pack next to one another more efficiently. The air permeability of these media is numerically simulated and discussed in detail with respect to the available 2D and 3D studies in the literature. Our permeability calculations show an excellent agreement with the predictions of the empirical equation of Davies [1] as well as the analytical model of Spielman and Goren [2]. Such an agreement indicates that, within the range of dimensions considered, the fiber length has no significant influence on the materials' through-plane permeability as long as the SVF remains constant. While this concept has been empirically observed in the past, our work is the first numerical simulation devised to confirm it.}, number={8}, journal={MODELLING AND SIMULATION IN MATERIALS SCIENCE AND ENGINEERING}, author={Wang, Q. and Maze, B. and Tafreshi, H. Vahedi and Pourdeyhimi, B.}, year={2007}, month={Dec}, pages={855–868} }
 @inproceedings{maze_vahedi tafreshi_wang_pourdeyhimi_2007, title={Simulation of nanoparticle filtration via nanofiber media at reduced operating pressures}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-52649145930&partnerID=MN8TOARS}, booktitle={International Nonwovens Technical Conference, INTC 2007: Joint INDA-TAPPI Conference}, author={Maze, B. and Vahedi Tafreshi, H. and Wang, Q. and Pourdeyhimi, B.}, year={2007}, pages={665–669} }
 @inproceedings{maze_vahedi tafreshi_pourdeyhimi_2007, title={Simulation of nanoparticle filtration via nanofiber media at reduced operating pressures}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84902668697&partnerID=MN8TOARS}, booktitle={Fiber Society 2007 Spring Conference - Advanced Polymer Fiber Materials Science and its Applications in Novel Engineered Products}, author={Maze, B. and Vahedi Tafreshi, H. and Pourdeyhimi, B.}, year={2007} }
 @inproceedings{maze_vahedi tafreshi_wang_pourdeyhimi_2007, title={Unsteady-state simulation of nanoparticle filtration via electrospun nanofiber webs at reduced operating pressures}, volume={2}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84883769610&partnerID=MN8TOARS}, booktitle={American Filtration and Separations Society - 20th Annual Conference and Exposition of the American Filtration and Separations Society 2007}, author={Maze, B. and Vahedi Tafreshi, H. and Wang, Q. and Pourdeyhimi, B.}, year={2007}, pages={1014–1018} }
 @article{wang_maze_tafreshi_pourdeyhimi_2006, title={A case study of simulating submicron aerosol filtration via lightweight spun-bonded filter media}, volume={61}, ISSN={["1873-4405"]}, DOI={10.1016/j.ces.2006.03.039}, abstractNote={The most common method of filtration is via fibrous nonwoven media. Fibrous filters are generally characterized by their collection efficiency and pressure drop. Traditional computational studies in this area are typically based on unrealistic 2-D geometries with the fibers simply placed in a lattice (regular array) perpendicular to the flow. The traditional approaches however, do not permit studying the relation between the 3-D structure of a filter media and its performance. In this study, for the first time, a virtual 3-D web is generated based on the fiber orientation information obtained from analyzing microscopic images of lightweight spun-bonded filter media. Pressure drop and collection efficiency of our virtual filter are simulated and compared with the previous 2-D analytical and numerical models as well as experiment. Our pressure drop calculation, unlike the previous models, showed a perfect agreement with the predictions of the Davies' empirical equation. The collection efficiencies obtained from simulating a thin spun-bonded filter media challenged with submicron particles having diameters ranging from 50 to 500 nm showed a similar trend as that of the previous 2-D models. For the solid volume fraction (SVF), filter thickness, and the fiber and particle diameters considered in this study, we found collection efficiencies higher than that of the above mentioned 2-D models with a relatively good agreement with experimental data obtained from a TSI 8130 filter tester.}, number={15}, journal={CHEMICAL ENGINEERING SCIENCE}, author={Wang, Q. and Maze, B. and Tafreshi, H. Vahedi and Pourdeyhimi, B.}, year={2006}, month={Aug}, pages={4871–4883} }
 @article{wang_maze_tafreshi_pourdeyhimi_2006, title={A note on permeability simulation of multifilament woven fabrics}, volume={61}, ISSN={["1873-4405"]}, DOI={10.1016/j.ces.2006.09.043}, abstractNote={A conventional approach for modeling permeability of multifilament fabrics is to consider their warps and wefts to be individual thick filament made of homogeneous porous media and solve the flow equations for such monofilament fabrics. In this work, for the first time, the full 3-D geometry of an idealized multifilament woven fabric, wherein the filaments are packed in hexagonal arrangement, is generated to compute its permeability and compare with the homogeneous anisotropic lumped model of Gebart (1992. Permeability of unidirectional reinforcements for RTM. Journal of Composite Materials 26(8), 1100–1133). While a relatively good agreement is obtained, our results indicate that Gebart's model slightly underestimate the permeability of multifilament fabrics even at high yarn's solid volume fractions.}, number={24}, journal={CHEMICAL ENGINEERING SCIENCE}, author={Wang, Q. and Maze, B. and Tafreshi, H. Vahedi and Pourdeyhimi, B.}, year={2006}, month={Dec}, pages={8085–8088} }
 @article{anantharamaiah_tafreshi_pourdeyhimi_2006, title={A study on flow through hydroentangling nozzles and their degradation}, volume={61}, ISSN={["1873-4405"]}, DOI={10.1016/j.ces.2006.01.038}, abstractNote={Abstract Hydroentangling is a technique for mechanically bonding loose filaments or fibers arranged in a web. The efficiency with which the web is entangled depends on the peculiar properties of laminar high-speed waterjets used. The characteristics of such waterjets strongly depend on the operating pressure and the nozzle inlet sharpness which influence the dynamics of fluid flow. In this study, we report on experiments and CFD simulations aimed at improving our knowledge of such two-phase flows. In particular, we simulate the formation and growth of the cavitation cloud inside a sharp-edge hydroentangling nozzle at pressures ranging from 10 to 200 bars ( 5700 Re 25 600 ) . Our experimental results run at the same pressures, confirm that nozzle cavitation will cause “hydraulic flip”. Once hydraulic flip occurs, atomizing waterjets will turn into constricted laminar waterjets with long intact lengths—a necessary condition for hydroentangling. It has been observed that the nozzle inlet deteriorates under high pressures. Our CFD simulations show a striking similarity between the contours of shear stress at the nozzle inlet and the nozzle wear pattern. These findings together with the SEM elemental analysis at the nozzle inlet reveal the potential for metal oxidation around the inlet, implicating stress-induced corrosion as a major contributor to the nozzle wear. Cavitation might also be one of the mechanisms responsible for the above-mentioned wear at the inlet edge. Additionally, our water-borne solid particle tracking, confirms SEM experimental results that particle deposition can potentially play a considerable role in the deterioration of the nozzle inlet shape.}, number={14}, journal={CHEMICAL ENGINEERING SCIENCE}, author={Anantharamaiah, N. and Tafreshi, H. Vahedi and Pourdeyhimi, B.}, year={2006}, month={Jul}, pages={4582–4594} }
 @article{anantharamaiah_tafreshi_pourdeyhimi_2006, title={A study on hydroentangling waterjets and their impact forces}, volume={41}, ISSN={["1432-1114"]}, DOI={10.1007/s00348-006-0162-5}, number={1}, journal={EXPERIMENTS IN FLUIDS}, author={Anantharamaiah, N. and Tafreshi, H. Vahedi and Pourdeyhimi, B.}, year={2006}, month={Jul}, pages={103–113} }
 @article{wang_maze_vahedi tafreshi_pourdeyhimi_2006, title={Approaches for predicting collation efficiency of fibrous filters}, volume={5}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-33749549286&partnerID=MN8TOARS}, number={2}, journal={Journal of Textile and Apparel, Technology and Management}, author={Wang, Q. and Maze, B. and Vahedi Tafreshi, H. and Pourdeyhimi, B.}, year={2006} }
 @article{tafreshi_ercan_pourdeyhimi_2006, title={Calculating mass transfer from vertical wet fabrics using a free convection heat transfer correlation}, volume={42}, ISSN={["1432-1181"]}, DOI={10.1007/s00231-005-0050-1}, number={9}, journal={HEAT AND MASS TRANSFER}, author={Tafreshi, H. Vahedi and Ercan, E. and Pourdeyhimi, B.}, year={2006}, month={Jul}, pages={767–769} }
 @misc{wegner_piseri_tafreshi_milani_2006, title={Cluster beam deposition: a tool for nanoscale science and technology}, volume={39}, ISSN={["1361-6463"]}, url={https://publons.com/wos-op/publon/6333204/}, DOI={10.1088/0022-3727/39/22/r02}, abstractNote={Gas phase nanoparticle production, manipulation and deposition is of primary importance for the synthesis of nanostructured materials and for the development of industrial processes based on nanotechnology. In this review we present and discuss this approach, introducing cluster sources, nanoparticle formation and growth mechanisms and the use of aerodynamic focusing methods that are coupled with supersonic expansions to obtain high intensity cluster beams with a control on nanoparticle mass and spatial distribution. The implication of this technique for the synthesis of nanostructured materials is also presented and applications are highlighted.}, number={22}, journal={JOURNAL OF PHYSICS D-APPLIED PHYSICS}, author={Wegner, K. and Piseri, P. and Tafreshi, H. Vahedi and Milani, P.}, year={2006}, month={Nov}, pages={R439–R459} }
 @inproceedings{latifi_vahedi tafreshi_pourdeyhimi_2006, title={Fiber dispersion in wet-lay mixing tanks}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-36049022222&partnerID=MN8TOARS}, booktitle={International Nonwovens Technical Conference, INTC 2006}, author={Latifi, M. and Vahedi Tafreshi, H. and Pourdeyhimi, B.}, year={2006}, pages={384–389} }
 @inproceedings{anantharamaiah_roempert_tafreshi_pourdeyhimi_2006, title={Hydroentangling - A Path to Technical Nonwovens}, booktitle={TechTextil}, author={Anantharamaiah, N. and Roempert, K. and Tafreshi, H.V. and Pourdeyhimi, B.}, year={2006}, month={Mar} }
 @inproceedings{wang_maze_tafreshi_pourdeyhimi_2006, title={Nanoparticle Filtration by Virtual Nonwoven Media}, author={Wang, Q. and Maze, B. and Tafreshi, H.V. and Pourdeyhimi, B.}, year={2006}, month={May} }
 @article{anantharamaiah_tafreshi_pourdeyhimi_2006, title={Numerical simulation of the formation of constricted waterjets in hydroentangling nozzles - Effects of nozzle geometry}, volume={84}, ISSN={["1744-3563"]}, DOI={10.1205/cherd.05077}, abstractNote={The role of nozzle geometry on the formation of constricted waterjets, waterjets that are detached from the wall throughout the nozzle, is considered in this paper. Such waterjets have found applications in various industries, including nonwoven processing. Due to the very small time and length scales involved in high-speed flow through micronozzles, experimental observation of the jet formation is cumbersome if not impossible. Computer simulation, on the other hand, can improve our understanding of the waterjet formation process under such conditions. In this paper, we report on flow simulations of water through sharp-edge cone-capillary nozzles having a diameter of 128 mm at different Reynolds numbers. Unsteady-state laminar two-phase flow is considered in axisymmetric nozzles with different capillary lengths. Our simulations show the separation of the flow from the nozzle wall as it enters the orifice. Simulations have also revealed that flow reattachment occurs in cases where the nozzle capillary length is longer than a critical length. For sharpedge nozzles operating at high Reynolds numbers, the critical capillary length is found to be about 70% of the nozzle diameter. Nozzles with a capillary length less than the above critical length produce a constricted waterjet with no apparent cavitation during the jet formation.}, number={A3}, journal={CHEMICAL ENGINEERING RESEARCH & DESIGN}, author={Anantharamaiah, N. and Tafreshi, H. Vahedi and Pourdeyhimi, B.}, year={2006}, month={Mar}, pages={231–238} }
 @inproceedings{zobel_maze_tafreshi_pourdeyhimi_2006, title={Permeability of Highly Dense Nonwoven Fabrics}, booktitle={International Nonwoven Technical Conference (INTC 2006)}, author={Zobel, S. and Maze, B. and Tafreshi, H.V. and Pourdeyhimi, B.}, year={2006}, month={Sep} }
 @inproceedings{anantharamaiah_tafreshi_pourdeyhimi_2006, title={Predicting Inlet Roundness of Hydroentangling Nozzles Using CFD Simulations}, booktitle={International Nonwoven Technical Conference (INTC 2006)}, author={Anantharamaiah, N. and Tafreshi, H.V. and Pourdeyhimi, B.}, year={2006}, month={Sep} }
 @article{pourdeyhimi_mazé_tafreshi_2006, title={Simulation and Analysis of Unbonded Nonwoven Fibrous Structures}, volume={1}, ISSN={1558-9250 1558-9250}, url={http://dx.doi.org/10.1177/155892500600100204}, DOI={10.1177/155892500600100204}, abstractNote={ In this work we report on our algorithm for generating 3–D virtual structures resembling un-bonded fibrous webs. The paper discusses short and infinitely long fibers, each emulating a category of nonwoven fibrous medium. The structure Solid Volume Fraction (SVF), being the most important characteristic of a fibrous porous medium, is calculated for different fiberwebs and discussed in details. It is shown that the SVF of the fibrous structures generated by our algorithm is independent of the basis weight. In other words, the porosity of the medium is only a function of the fiber properties – this is as expected. It is also demonstrated that by decreasing the fiber diameter while keeping other properties of the virtual fiberweb constant causes the SVF to decrease almost linearly. The same is not observed for the fiber rigidity. The capability of our algorithm for generating fibrous webs made up of layers of different fibers is demonstrated and their properties are discussed. The application of such virtual fibrous structures in modeling transport phenomena in nonwoven materials and their potential applications in load-deformation studies are discussed. }, number={2}, journal={Journal of Engineered Fibers and Fabrics}, publisher={SAGE Publications}, author={Pourdeyhimi, Behnam and Mazé, Benoit and Tafreshi, Hooman Vahedi}, year={2006}, month={Jun}, pages={155892500600100} }
 @inproceedings{anantharamaiah_roempert_tafreshi_pourdeyhimi_2006, title={The Role of Waterjet Curtain in Modifying the Jet Streaks in Hydroentangling}, booktitle={International Nonwoven Technical Conference (INTC 2006)}, author={Anantharamaiah, N. and Roempert, K. and Tafreshi, H.V. and Pourdeyhimi, B.}, year={2006}, month={Sep} }
 @article{vahedi tafreshi_piseri_benedek_milani_2006, title={The role of gas dynamics in operation conditions of a puised microplasma cluster source for nanostructured thin films deposition}, volume={6}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-33745627534&partnerID=MN8TOARS}, DOI={10.1166/jnn.2006.139}, abstractNote={This study intends to explain the fluid dynamic characteristics of a Pulsed Microplasma Cluster Source (PMCS). An axially symmetric steady state simulation is performed for modeling the real-life three-dimensional unsteady flow of hypersonic helium inside our PMCS. Hypersonic helium flow is simulated using Realizable k-epsilon turbulent model. We obtained the jet velocity, density, and pressure field inside our PMCS for the conditions considered and discussed them with respect to our experimental observations. We also presented a qualitative discussion on the formation-termination process of this hypersonic jet. In particular, simulation, in agreement with the experiment, indicates that the middle stage of the injection process, where the Mach disk stands close to the ablation target and at the same time the mass flow rate is relatively high, is almost the appropriate time for firing the electric discharge. We simulated the jet-electrode impingement and tracked the trajectory of the ablated carbon clusters, considered as rigid spheres, inside the PMCS. We noticed that the spatial distribution of the clusters inside PMCS is highly conserved during the free expansion of the cluster beam out of the nozzle (in the vacuum chambers) and is recognizable in the deposited carbon film. This indicates that the geometry of PMCS plays a significant role in the uniformity of the deposited film.}, number={4}, journal={Journal of Nanoscience and Nanotechnology}, author={Vahedi Tafreshi, H. and Piseri, P. and Benedek, G. and Milani, P.}, year={2006}, pages={1140–1149} }
 @inproceedings{anantharamaiah_tafreshi_pourdeyhimi_2005, title={A Study on Hydroentangling Waterjets}, booktitle={International Nonwoven Technical Conference (INTC 2005)}, author={Anantharamaiah, N. and Tafreshi, H.V. and Pourdeyhimi, B.}, year={2005}, month={Sep} }
 @misc{benedek_vahedi tafreshi_podesta’_milani_2005, title={FRACTAL GROWTH OF CARBON SCHWARZITES}, url={http://dx.doi.org/10.1142/9789812701558_0017}, DOI={10.1142/9789812701558_0017}, abstractNote={The potential energy, the thermodynamic properties and the growth conditions of random carbon schwarzites are theoretically investigated in connection with their topological properties and self-affine structure. An analysis based on numerical simulations of transmission electron microscopy images permits to assign certain carbon foams, recently produced by means of supersonic cluster beam deposition, to self-affine random schwarzites. It is shown that self-affinity makes their thermodynamic properties non-extensive. The fractal growth exponent is shown to be related to the parameter q -1 of the Tsallis non-extensive entropy.}, journal={Complexity, Metastability and Nonextensivity}, publisher={WORLD SCIENTIFIC}, author={Benedek, Giorgio and Vahedi Tafreshi, Hooman and Podesta’, Alessandro and Milani, Paolo}, year={2005}, month={Sep} }
 @inproceedings{tafreshi_maze_pourdeyhimi_2005, title={Water Flow Simulation in Nonwovens Made of Hydrophilic and Non-hydrophilic Fibers}, booktitle={Belt-wide Cotton Conference}, author={Tafreshi, H.V. and Maze, B. and Pourdeyhimi, B.}, year={2005}, month={Jan} }
 @inproceedings{tafreshi_pourdeyhimi_2004, title={A Study on Hydroentangling Impact Force}, booktitle={International Nonwovens Technical Conference (INTC 2004)}, author={Tafreshi, H.V. and Pourdeyhimi, B.}, year={2004}, month={Sep} }
 @article{tafreshi_pourdeyhimi_2004, title={Cavitation and Hydraulic Flip}, volume={13}, number={1}, journal={Fluent News}, author={Tafreshi, H.V. and Pourdeyhimi, B.}, year={2004}, pages={38} }
 @article{begenir_tafreshi_pourdeyhimi_2004, title={Effect of nozzle geometry on hydroentangling water jets: Experimental observations}, volume={74}, ISSN={["1746-7748"]}, DOI={10.1177/004051750407400215}, abstractNote={ This paper reports on the role of nozzle geometry on the characteristics of hydroen tangling water jets, specifically the behavior of three different conventional nozzle geometries under pressures below 3500 psi. Profiles of the water jets are digitized with a Nikon Dlx digital camera from which we extract the water-jet breakup lengths and spray angles under different operating conditions. Our preliminary data indicate that the cone-up nozzle produces water jets with considerably shorter intact lengths and slightly larger spray angles and a higher coefficient of discharge compared to the two other geometries considered. We attribute this distinct behavior to friction-induced and cavitation-induced turbulence inside the cone-up nozzles; a constricted water jet is formed by cone-down or cylindrical nozzles. Our results are in excellent agreement with previous experimental and computational data. }, number={2}, journal={TEXTILE RESEARCH JOURNAL}, author={Begenir, A and Tafreshi, HV and Pourdeyhimi, B}, year={2004}, month={Feb}, pages={178–184} }
 @inproceedings{tafreshi_maze_pourdeyhimi_2004, title={In-plane and Through-plane Liquid Flow Simulation in Nonwoven Glass Fiber Mats}, booktitle={International Nonwovens Technical Conference (INTC 2004)}, author={Tafreshi, H.V. and Maze, B. and Pourdeyhimi, B.}, year={2004}, month={Sep} }
 @misc{piseri_tafreshi_milani_2004, title={Manipulation of nanoparticles in supersonic beams for the production of nanostructured materials}, volume={8}, ISSN={["1879-0348"]}, DOI={10.1016/j.cossms.2004.08.002}, abstractNote={Production and manipulation of nanoparticles in the gas phase is of primary importance for the synthesis of nanostructured materials and for the development of industrial processes based on nanotechnology. In this review we will present and discuss the approach based on the use of aerodynamic focusing methods coupled to supersonic expansions to obtain high intensity cluster beams with a control on nanoparticle mass and spatial distribution. The implication of this techniques for the synthesis of nanostructured materials will be also presented.}, number={3-4}, journal={CURRENT OPINION IN SOLID STATE & MATERIALS SCIENCE}, author={Piseri, P and Tafreshi, HV and Milani, P}, year={2004}, pages={195–202} }
 @inproceedings{tafreshi_maze_pourdeyhimi_2004, title={Modeling Particle Filtration by Glass Fiber Filters}, booktitle={The Fiber Society Spring Symposium}, author={Tafreshi, H.V. and Maze, B. and Pourdeyhimi, B.}, year={2004}, month={Jun} }
 @inproceedings{tafreshi_maze_pourdeyhimi_2004, title={Modeling Submicron Particle Filtration by Virtual Glass Fiber Mats}, booktitle={Advances in Filtration & Separations Media}, author={Tafreshi, H.V. and Maze, B. and Pourdeyhimi, B.}, year={2004}, month={Nov} }
 @article{tafreshi_pourdeyhimi_2004, title={Simulating cavitation and hydraulic flip inside hydroentangling nozzles}, volume={74}, DOI={10.1177/004051750407400413}, abstractNote={ Hydroentangling owes its success to the peculiar properties of coherent water jets. For hydroentangling to be feasible at higher pressures, it is extremely important that water jets maintain their collimation for an appreciable distance downstream of the nozzle. How ever, water-jet breakup accelerates at high pressures. Recent studies have shown that cavitation severely affects the integrity of high-pressure water jets. Investigating cavita tion experimentally is not trivial. Computational fluid dynamics simulations offer appro priate tools as a first step. This paper discusses the results of an unsteady-state simulation, which shows the inception and time-evolution of a cavitation cloud inside a hydroentan gling nozzle. Under certain conditions, the cavity cloud extends to the nozzle outlet, resulting in the so-called hydraulic flip. Once hydraulic flip occurs, cavitation suddenly vanishes because the downstream air moves upward into the nozzle and fills the cavity. This air envelops the water flow inside the nozzle, which results in the depletion of cavitation-induced instabilities from the jet surface and elongates the jet breakup length. Moreover, our simulations reveal the approximate time scales of cavity growth through the nozzle. This information is highly relevant for experimental visualization of nozzle cavitation. The discharge and velocity coefficient obtained from the simulation are in a good agreement with published experimental data. }, number={4}, journal={Textile Research Journal}, author={Tafreshi, H. V. and POURDEYHIMI, BEHNAM}, year={2004}, pages={359–364} }
 @article{vahedi tafreshi_pourdeyhimi_2004, title={Simulating cavitation and hydraulic flip inside hydroentangling nozzles}, volume={74}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0345722190&partnerID=MN8TOARS}, number={4}, journal={Textile Research Journal}, author={Vahedi Tafreshi, H. and Pourdeyhimi, B.}, year={2004}, pages={359–364} }
 @article{simulating cavitation and hydraulic flip inside hydroentangling nozzles_2004, url={https://publons.com/wos-op/publon/65200209/}, journal={Textile Research Journal}, year={2004} }
 @inproceedings{tafreshi_pourdeyhimi_2003, title={A Study on Cavitation inside Hydroentangling Nozzles}, booktitle={International Nonwovens Technical Conference (INTC 2003)}, author={Tafreshi, H.V. and Pourdeyhimi, B.}, year={2003}, month={Sep} }
 @inproceedings{tafreshi_pourdeyhimi_2003, title={Gas-particle decoupling by nozzle-induced aerodynamic effects}, booktitle={American Filtration and Separation Society}, author={Tafreshi, H.V. and Pourdeyhimi, B.}, year={2003}, month={Jun} }
 @article{vahedi tafreshi_pourdeyhimi_2003, title={Role of baffles on flow fields inside wet-lay mixing tanks and their pontential influence on fiber dispersion}, volume={73}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0041339609&partnerID=MN8TOARS}, number={7}, journal={Textile Research Journal}, author={Vahedi Tafreshi, H. and Pourdeyhimi, B.}, year={2003}, pages={575–582} }
 @article{tafreshi_pourdeyhimi_2003, title={Role of baffles on flow fields inside wet-lay mixing tanks and their potential influence on fiber dispersion}, volume={73}, DOI={10.1177/004051750307300703}, abstractNote={ Dispersion and separation of fiber bundles requires exposing them to a shear stress field to overcome interfiber frictional forces. To this end, fiber-mixing tanks are equipped with baffles to enhance shear and agitation in the water to help disperse the fiber bundles. The time and agitation required to separate and disperse the fibers depends on the fibers being used. It is well known, however. that excessive agitation will give rise to the formation of rope defects in the output because of the high-energy vortices that form behind these baffles. Optimizing the baffle geometry and position is therefore critically important in the wet-lay process. This paper presents some possible ways of eliminating the regions in the water velocity field where strong vortices may be present: in particular, the motivation for this paper is that minimizing vortex formation will lower the probability of rope forma tion. In this regard, we present a series of numerical simulations to model fluid-flow behavior inside wet-lay mixing tanks. A turbulent flow field is obtained by solving the Navier-Stokes equations in a two-dimensional geometry. The turbulent features of the flow are captured using the RNG k-e model. Fibers, modeled as spherical rigid particles with the same volume as the fibers, are introduced into the solution domain and their trajectories are tracked inside the mixing tank. The effects of the baffles and their orientation with respect to flow streamlines are simulated. We report the simulation results for different baffle configurations and show that aligning the baffles with the streamlines and increasing their surface area can eliminate the formation of vortices while still keeping the shear field at a satisfactory level. We hypothesize that eliminating the vortices in the mixing tank reduces the probability of rope formation, but this hypothesis needs to be verified experimentally. }, number={7}, journal={Textile Research Journal}, author={Tafreshi, H. V. and POURDEYHIMI, BEHNAM}, year={2003}, pages={575–582} }
 @article{role of baffles on flow fields inside wet-lay mixing tanks and their potential influence on fiber dispersion_2003, url={https://publons.com/wos-op/publon/65200206/}, journal={Textile Research Journal}, year={2003} }
 @article{tafreshi_pourdeyhimi_holmes_shiffler_2003, title={Simulating and characterizing water flows inside hydroentangling orifices}, volume={73}, ISSN={["0040-5175"]}, DOI={10.1177/004051750307300310}, abstractNote={ The hydroentangling technique uses cone-capillary orifice nozzles to direct high-energy water jets against loose fiber webs. This study simulates the effects of orifice configuration on the water-jet properties. An axisymmetric steady-state model is considered for this two-phase system. The turbulent water jet is simulated using a realizable k - ε model, and the behaviors of cone-up and cone-down geometries are investigated. The simulation reveals that the water jet produced by a cone-up orifice keeps contact with the walls all the way through the orifice and may undergo cavitation to reduce the water-jet intact length and damage to the orifice surface. In contrast, the cone-down geometry can form a constricted water jet that is enveloped by an air gap, which separates the water from the orifice surface and therefore prevents cavitation. The results are in excellent agreement with previous experimental studies. }, number={3}, journal={TEXTILE RESEARCH JOURNAL}, author={Tafreshi, HV and Pourdeyhimi, B and Holmes, R and Shiffler, D}, year={2003}, month={Mar}, pages={256–262} }
 @article{tafreshi_pourdeyhimi_2003, title={Simulating the flow dynamics in hydroentangling nozzles: Effect of cone angle and nozzle aspect ratio}, volume={73}, ISSN={["0040-5175"]}, url={https://publons.com/wos-op/publon/65200207/}, DOI={10.1177/004051750307300807}, abstractNote={ Flow behavior in various nozzle shapes from the hydroentangling cone-capillary family is modeled in this paper. The work studies the effects of cone angle and nozzle aspect ratio (the ratio of the capillary section to its diameter) on water-jet formation. In particular, two sets of nozzles are considered. The first set consists of nozzles that have an aspect ratio of one and cone angles of 19, 15, 11, 7, and 3°, respectively. The nozzles in the second set have their inlet and outlet diameters fixed, but their aspect ratios vary from 1 to 6. The results from a two-phase axisymmetric steady-state model of turbulent nozzle flow reveal that decreasing the cone angle or increasing the nozzle aspect ratio does not affect the hydroentangling water-jet characteristics. The computational scheme is validated by comparing part of the results with the available experimental data in the literature. }, number={8}, journal={TEXTILE RESEARCH JOURNAL}, author={Tafreshi, HV and Pourdeyhimi, B}, year={2003}, month={Aug}, pages={700–704} }
 @article{vahedi tafreshi_pourdeyhimi_2003, title={Simulating the flow dynamics in hydroentangling nozzles: Effect of cone angle and nozzle aspect ratio}, volume={73}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0042731538&partnerID=MN8TOARS}, number={8}, journal={Textile Research Journal}, author={Vahedi Tafreshi, H. and Pourdeyhimi, B.}, year={2003}, pages={700–704} }
 @inproceedings{tafreshi_begenir_pourdeyhimi_2003, title={The Role of Nozzle Design in Characteristics of the Hydroentangling Waterjets}, booktitle={16th Annual Conference on Liquid Atomization and Spray Systems (ILASS Americas)}, author={Tafreshi, H.V. and Begenir, A. and Pourdeyhimi, B.}, year={2003}, month={May} }
 @inproceedings{begenir_tafreshi_pourdeyhimi_2003, title={The Role of Nozzle Design in Characteristics of the Hydroentangling Waterjets: Experimental Study}, booktitle={International Nonwovens Technical Conference (INTC 2003)}, author={Begenir, A. and Tafreshi, H.V. and Pourdeyhimi, B.}, year={2003}, month={Sep} }
 @article{tafreshi_pourdeyhimi_2003, title={The effects of nozzle geometry on waterjet breakup at high Reynolds numbers}, volume={35}, ISSN={["0723-4864"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0345329521&partnerID=MN8TOARS}, DOI={10.1007/s00348-003-0685-y}, number={4}, journal={EXPERIMENTS IN FLUIDS}, author={Tafreshi, HV and Pourdeyhimi, B}, year={2003}, month={Oct}, pages={364–371} }
 @article{benedek_vahedi-tafreshi_barborini_piseri_milani_ducati_robertson_2003, title={The structure of negatively curved spongy carbon}, volume={12}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0038184103&partnerID=MN8TOARS}, DOI={10.1016/S0925-9635(03)00082-7}, abstractNote={This work reports on the production and characterization of a novel form of nanostructured carbon consisting of three-dimensional, fully connected sp2 networks. This form of carbon is characterized by interconnected thin layers forming a spongy structure with meso- and macroporosity. The spongy carbon is produced by a pulsed microplasma cluster source in the presence of a metal–organic catalyst and it can be deposited as a film by supersonic cluster beam deposition (SCBD). Unlike fullerenes, nanotubes and graphite, which consist of zero-, one- or two-dimensional covalent objects held together by van der Waals’ forces, this novel structure consists of a robust, multiply connected graphene sheet which is fully covalent in three dimensions. Theoretical analysis indicates that such carbon sponges apparently grow as minimal surfaces and have the long-sought topological structure of random schwarzites.}, number={3-7}, journal={Diamond and Related Materials}, author={Benedek, G. and Vahedi-Tafreshi, H. and Barborini, E. and Piseri, P. and Milani, P. and Ducati, C. and Robertson, J.}, year={2003}, pages={768–773} }
 @article{tafreshi_benedek_piseri_vinati_barborini_milani_2002, title={A Simple Nozzle Configuration for the Production of Low Divergence Supersonic Cluster Beam by Aerodynamic Focusing}, volume={36}, ISSN={0278-6826 1521-7388}, url={http://dx.doi.org/10.1080/02786820252883838}, DOI={10.1080/02786820252883838}, abstractNote={A nozzle configuration for the production of an intense and collimated supersonic cluster beam is presented and characterized by numerical modeling. A simple lens added to a cylindrical nozzle exploits aerodynamic focusing effects. The effect of the focalizing nozzle is an enrichment of the core of the jet with clusters of an arbitrary size interval depending on carrier gas pressure and temperature. The influence of the source and nozzle geometrical parameters and of the expansion conditions on the cluster focalization is simulated and compared to the experimental results. A collimating effect on particle velocities and the possibility of obtaining a cluster mass selection is also observed.}, number={5}, journal={Aerosol Science and Technology}, publisher={Informa UK Limited}, author={Tafreshi, H. Vahedi and Benedek, G. and Piseri, P. and Vinati, S. and Barborini, E. and Milani, P.}, year={2002}, month={May}, pages={593–606} }
 @inproceedings{tafreshi_piseri_milani_2002, title={A Simulation on the Effect of Brownian Motion on Nanoparticle Transport in a Pulsed Micro-plasma Cluster Source}, booktitle={Annual Conference of the American Association for Aerosol Research (AAAR)}, author={Tafreshi, H.V. and Piseri, P. and Milani, P.}, year={2002}, month={Oct} }
 @article{tafreshi_benedek_zamankhan_sarkomaa_2002, title={Diffusive behavior and structural characterization of a hard-sphere fluid through a narrow channel with roughened walls}, volume={80}, ISSN={["1208-6045"]}, DOI={10.1139/P02-016}, abstractNote={ A molecular dynamics technique is devised to simulate the flow of a hard-sphere fluid between two parallel roughened walls separated by a 10 particle diameter distance. The structural state of the system in different solid-volume fractions is characterized by analyzing the static-structure factor contour plot. At solids concentrations below [Formula: see text] [Formula: see text] 0.3, the calculations have shown no remarkable signature of the presence of the roughened confining walls similar to the previous unbounded simulation results (wide channel). At high concentrations, walls manifest their presence by reducing the particle diffusion in the direction of velocity gradient. Due to the metastability of the assembly, further increase in the solid fraction, [Formula: see text] [Formula: see text] 0.6, may yield a crystalline phase wherein diffusion coefficients vanish locally. }, number={7}, journal={CANADIAN JOURNAL OF PHYSICS}, author={Tafreshi, H and Benedek, G and Zamankhan, P and Sarkomaa, P}, year={2002}, month={Jul}, pages={723–731} }
 @inproceedings{di fonzo_piseri_tafreshi_milani_2002, title={Nano-cluster Beam Focusing in an Aerodynamic Lens System}, booktitle={Annual Conference of the American Association for Aerosol Research (AAAR)}, author={Di Fonzo, F. and Piseri, P. and Tafreshi, H.V. and Milani, P.}, year={2002}, month={Oct} }
 @inproceedings{tafreshi_pourdeyhimi_holmes_shiffler_2002, title={Numerical Investigation on the Waterjets Issued by Hydroentangling Orifice Nozzles}, booktitle={International Nonwovens Technical Conference (INTC 2002)}, author={Tafreshi, H.V. and Pourdeyhimi, B. and Holmes, R. and Shiffler, D.}, year={2002}, month={Sep} }
 @inproceedings{tafreshi_pourdeyhimi_2002, title={Numerical Simulation of Hydroentangling Orifice Flow}, booktitle={The Fiber Society}, author={Tafreshi, H.V. and Pourdeyhimi, B.}, year={2002}, month={Oct} }
 @article{tafreshi_piseri_barborini_benedek_milani_2002, title={Simulation on the effect of Brownian motion on nanoparticle trajectories in a pulsed microplasma cluster source}, volume={4}, ISSN={["1572-896X"]}, DOI={10.1023/A:1022845401781}, number={6}, journal={JOURNAL OF NANOPARTICLE RESEARCH}, author={Tafreshi, HV and Piseri, P and Barborini, E and Benedek, G and Milani, P}, year={2002}, month={Dec}, pages={511–524} }
 @inproceedings{tafreshi_pourdeyhimi_2002, title={The Role of Baffles in Fiber Dispersion in Mixing Tanks}, booktitle={The Fiber Society}, author={Tafreshi, H.V. and Pourdeyhimi, B.}, year={2002}, month={Oct} }
 @article{vahedi tafreshi_benedek_piseri_vinati_barborini_milani_2001, title={Aerodynamic focusing of clusters into a high intensity and low divergence supersonic beam}, volume={16}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0346312280&partnerID=MN8TOARS}, number={2}, journal={EPJ Applied Physics}, author={Vahedi Tafreshi, H. and Benedek, G. and Piseri, P. and Vinati, S. and Barborini, E. and Milani, P.}, year={2001}, pages={149–156} }
 @inproceedings{tafreshi_piseri_vinati_barborini_benedek_milani_2001, title={Manipulation of Clusters in Supersonic Beams by Simple Aerodynamic Effects: a Novel Tool for Nanostructured Material Synthesis}, booktitle={International Symposium on Cluster Assembled Materials, IPAP Conference Series 3}, author={Tafreshi, H.V. and Piseri, P. and Vinati, S. and Barborini, E. and Benedek, G. and Milani, P.}, year={2001}, month={Jun}, pages={1–6} }
 @article{manipulation of clusters in supersonic beams by simple aerodynamic effects: a novel tool for nanostructured material synthesis_2001, url={https://publons.com/wos-op/publon/6333256/}, journal={Proceedings of the International Symposium on Cluster Assembled Materials}, year={2001} }
 @inproceedings{piseri_podesta_barborini_vinati_tafreshi_milani_2001, title={Production and Characterization of Highly Intense and Collimated Cluster Beams by Inertial Focusing in Supersonic Expansions}, booktitle={Molecular Beam Conference}, author={Piseri, P. and Podesta, A. and Barborini, E. and Vinati, S. and Tafreshi, H.V. and Milani, P.}, year={2001}, month={Jun} }
 @inproceedings{tafreshi_benedek_milani_2000, title={Simulation of Supersonic Cluster Beams for the Deposition of Nanostructured Films}, booktitle={National Conference on Physics of Matter (INFMeeting)}, author={Tafreshi, H.V. and Benedek, G. and Milani, P.}, year={2000}, month={Jun} }
 @inproceedings{tafreshi_benedek_piseri_barborini_milani_2000, title={Simulation of Supersonic Cluster Beams for the Deposition of Nanostructured Films I}, booktitle={Nozzle Design Study, Conference on High Performance Parallel Computing (CAPI 2000)}, author={Tafreshi, H.V. and Benedek, G. and Piseri, P. and Barborini, E. and Milani, P.}, year={2000}, month={Sep} }
 @article{bond-orientational order in sheared dense flows of inelastic hard spheres_1998, volume={73}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0010233091&partnerID=MN8TOARS}, DOI={10.1063/1.121896}, abstractNote={Three-dimensional bond-orientational order is studied using computer simulations with 4296 hard, monodisperse inelastic spheres flowing in a Couette geometry at a high shear rate. At an average volume fraction close to 0.6, a state with extended correlations in the orientations of particle clusters starts to develop for rough particles after sufficiently long run times. However, no clear evidence of crystallization is found in the system. Further tests of a sheared system comprised of smooth, inelastic spheres reveal crystallization consistent with the previous experimental observations.}, number={4}, journal={Applied Physics Letters}, year={1998}, pages={450–452} }
 @article{zamankhan_tafreshi_polashenski_sarkomaa_hyndman_1998, title={Shear induced diffusive mixing in simulations of dense Couette flow of rough, inelastic hard spheres}, volume={109}, ISSN={0021-9606 1089-7690}, url={http://dx.doi.org/10.1063/1.477076}, DOI={10.1063/1.477076}, abstractNote={Large-scale numerical simulations of a system of inelastic, rough, hard spheres of volume fraction φs=0.565, which are initially distributed randomly in a Couette geometry, show clear evidence of the movement of the particles in directions transverse to the bulk motion. This behavior of the aforementioned system, which has been considered as a model for a granular fluid, is consistent with recent experimental observations [Hsiau and Hunt, J. Fluid Mech. 251, 299 (1993)]. Based on the results obtained, there are indications that a bounded rapid granular flow could be a diffusive system at volume fractions even higher than 0.56. This finding contradicts earlier computer experiments [Campbell, J. Fluid Mech. 348, 85 (1997)] which found a rapidly flowing granular material is a diffusive system except at large solids concentrations (i.e., φs>0.56).}, number={11}, journal={The Journal of Chemical Physics}, publisher={AIP Publishing}, author={Zamankhan, Piroz and Tafreshi, Hooman Vahedi and Polashenski, William, Jr. and Sarkomaa, Pertti and Hyndman, Caroline L.}, year={1998}, month={Sep}, pages={4487–4491} }
 @article{zamankhan_polashenski_tafreshi_shakib manesh_sarkomaa_1998, title={Shear-induced particle diffusion in inelastic hard sphere fluids}, volume={58}, ISSN={1063-651X 1095-3787}, url={http://dx.doi.org/10.1103/physreve.58.r5237}, DOI={10.1103/physreve.58.r5237}, abstractNote={A large-scale numerical simulation of a system of inelastic, rough, hard spheres of volume fraction fS 50.565, starting from a disordered configuration in a Couette geometry, shows a transition to a layered state, which possesses long-range orientation order, after long run times. This phase transition is shown to cause a dramatic decay of the long-time transverse self-diffusion coefficient of particles. As the solid volume fraction is increased to 0.58, the dimensionless transverse self-diffusion coefficient decays further, approaching a value of order 10, which indicates structural arrest. @S1063-651X~98!50811-2#}, number={5}, journal={Physical Review E}, publisher={American Physical Society (APS)}, author={Zamankhan, Piroz and Polashenski, William and Tafreshi, Hooman Vahedi and Shakib Manesh, Amir and Sarkomaa, Pertti J.}, year={1998}, month={Nov}, pages={R5237–R5240} }
 @article{zamankhan_tafreshi_chen_1997, title={Lateral diffusive migration of massive particles in high-velocity vertical pipe flow of moderately dense gas-solid suspensions}, volume={56}, ISSN={1063-651X 1095-3787}, url={http://dx.doi.org/10.1103/physreve.56.2972}, DOI={10.1103/physreve.56.2972}, abstractNote={Transport processes involved in a gas-particle flow, comprised of spherical particles with a narrow size distribution suspended in a turbulent gas, are investigated theoretically on the basis of the recently developed Enskog theory for multicomponent dense mixtures of slightly smooth inelastic spherical particles @P. Zamankhan, Phys. Rev. E52, 4877~1995!#. The generalized Boltzmann equation of the previous work is modified to incorporate the relevant forces exerted upon individual particles including the drag force by the relative gas motion. Extending the method of moments of Grad @Commun. Pure Appl. Math. 2, 331 ~1949!#, the modified Boltzmann equation is solved to obtain the nonequilibrium velocity distribution function for particles of each size. By taking the monodisperse limit, a basic equation is derived for the treatment of the problem of lateral diffusive migration of solids in an assembly composed of separate equisized spherical particles traveling in a fully developed, turbulent upward flow of a gas within a vertical pipe. At moderately high solid concentrations, where the random component of the particle velocity is generated mainly by particle-particle collisions, the particle diffusivity and the thermal diffusion coefficient are found to increase with the square root of the granular temperature, a term that measures the energy of the random motion of the particles. @S1063-651X~97!07309-1#}, number={3}, journal={Physical Review E}, publisher={American Physical Society (APS)}, author={Zamankhan, Piroz and Tafreshi, Hooman and Chen, John}, year={1997}, month={Sep}, pages={2972–2980} }