@article{fan_li_pointer_bolotnov_2022, title={High-fidelity pool boiling simulations on multiple nucleation sites using interface capturing method}, volume={399}, ISSN={["1872-759X"]}, DOI={10.1016/j.nucengdes.2022.112004}, abstractNote={Boiling has proved to be one of the most efficient means for heat transfer and is a very important phenomenon during severe accident scenarios in light water reactors. High-fidelity pool boiling simulations can provide a numerical database for improving mechanistic boiling models by allowing for specific evaluation of interactions among bubbles. Previously published pool boiling simulations investigated two nucleation sites in which bubble growth at one site suppressed nucleation at the other site. Based on previous study results, more complicated interface-capturing simulations on pool boiling were conducted using PHASTA code with locally refined unstructured mesh. First, different boundary conditions (BCs) were assessed to support robustness and reproducibility of the boiling model. Then, a scale study was conducted at a larger domain with nine nucleation sites where either nine or four nucleation sites are activated. Involving more nucleation sites increased the complexity of bubble interactions from surrounding sites. Finally, bubble departure behavior influenced by wall heat flux was investigated. When heat flux was increased, the order of bubble departure changed, but diagonal bubbles always departed after one another. The departure time interval between the first and second bubble reduced as heat flux increased. The corresponding frequency was almost linearly proportional to the heat flux. In addition, bubble departure behavior was found to be greatly influenced by the nucleation site pattern. Multiple nucleation sites resulted in superimposed inhibitive effects from surrounding sites to each bubble, which extensively delayed the departure. This new observation was not discussed in previously published works. The work presented here provides new insight on the fundamental understanding of boiling phenomena, contributes to the development of a 3D multiphase computational fluid dynamics (M-CFD) model, and provides a more comprehensive database for data-driven pool boiling studies.}, journal={NUCLEAR ENGINEERING AND DESIGN}, author={Fan, Yuqiao and Li, Mengnan and Pointer, William D. and Bolotnov, Igor A.}, year={2022}, month={Dec} }
 @misc{fang_cambareri_li_saini_bolotnov_2020, title={Interface-Resolved Simulations of Reactor Flows}, volume={206}, ISSN={["1943-7471"]}, DOI={10.1080/00295450.2019.1620056}, abstractNote={Abstract This critical review paper outlines the recent progress in high-resolution numerical simulations of two-phase coolant flow in light water reactor–relevant geometries by resolving the water-vapor interface. Rapid development of capabilities in high-performance computing is creating exciting opportunities to study complex reactor thermal-hydraulic phenomena. Today’s advances in thermal-hydraulic analysis and interface-resolved simulations will help pave the way to the next level of understanding of two-phase flow behavior in complex geometries. This paper consists of two major parts: (1) a brief review of direct numerical simulation and interface tracking simulation and (2) several opportunities in the near future to apply cutting-edge simulation and analysis capabilities to address the nuclear-related multiphase flow challenges. The first part will discuss typical computational methods used for the simulations and provide some examples of the past work as well as computational cost estimates and affordability of such simulations for research and industrial applications. In the second part specific application examples are discussed, from adiabatic bubbly flow simulations in pressurized water reactor subchannel geometry to the modeling of nucleate boiling. The uniqueness of this study lies in the specific focus on applications with nuclear engineering interest as well as new generation modeling and analysis methodologies. Together with the ever-growing computing power, the related large-scale two-phase flow simulations will become indispensable for the improved scientific understanding of complex two-phase flow phenomena in nuclear reactors under normal operation and postulated accident conditions.}, number={2}, journal={NUCLEAR TECHNOLOGY}, author={Fang, Jun and Cambareri, Joseph J. and Li, Mengnan and Saini, Nadish and Bolotnov, Igor A.}, year={2020}, month={Feb}, pages={133–149} }
 @article{li_bolotnov_2020, title={The evaporation and condensation model with interface tracking}, volume={150}, ISSN={["1879-2189"]}, DOI={10.1016/j.ijheatmasstransfer.2019.119256}, abstractNote={Interface tracking simulation (ITS) is one of the promising approaches to describe heat transfer of boiling phenomena and their underlying mechanisms. Better understanding and modeling of this process will benefit various engineering systems relying on two-phase heat transfer. The presented research implements, verifies and validates the modeling capability of the evaporation process using a massively parallel unstructured grid flow solver, PHASTA. The verification of the evaporation and condensation model has been performed by comparing the bubble growth rate with analytical solutions. Both pool boiling and flow boiling simulations are performed using this ITS evaporation and condensation model. The bubble nucleation frequency in pool boiling simulation is validated against experimentally-based correlations. The bubble evolution and growth rate are compared with experimental data to validate the model performance under flow boiling condition. The authors propose an innovative ITS based-boiling model which can conduct boiling simulation with 3D unstructured computational mesh. This capability will serve as one of the most important building blocks for high resolution boiling simulation in realistic engineering geometries being developed under the PHASTA simulation framework. Compared to the structured-grid-based solvers, which are challenging to apply to complex engineering geometries, this boiling model implementation is capable of conducting high-resolution boiling simulations in engineering geometries and resolving the detailed hydrodynamics and thermal information for quantities of interest at/around the interface. This approach may help fulfill the numerical data gap between the local physical phenomena and the engineering scale ITS applications in the future.}, journal={INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER}, author={Li, Mengnan and Bolotnov, Igor A.}, year={2020}, month={Apr} }
 @article{li_zeng_wonnell_bolotnov_2019, title={Development of a New Contact Angle Control Algorithm for Level-Set Method}, volume={141}, ISSN={["1528-901X"]}, DOI={10.1115/1.4041987}, abstractNote={A contact angle control algorithm is developed and implemented in the multiphase interface tracking flow solver—phasta. The subgrid force model is introduced to control the evolving contact angle. The contact angle force is applied when the current contact angle deviates from the desired value (or range of values) and decreases to zero when it reaches the desired value. The single bubble departure simulation and the capillary flat plates simulation are performed for verification purpose. The numerical results are compared with the analytical solution with good agreement. The mesh resolution sensitivity analysis and parametric study are conducted for both simulations. Coupled with the other existing capabilities in phasta like evaporation and condensation algorithm, the contact angle control algorithm will allow us to investigate the boiling phenomenon in various conditions with lower cost (by utilizing localized mesh refinement for bubble growth region) compared to uniformly refined structured meshes and in engineering geometries.}, number={6}, journal={JOURNAL OF FLUIDS ENGINEERING-TRANSACTIONS OF THE ASME}, author={Li, Mengnan and Zeng, Kaiyue and Wonnell, Louis and Bolotnov, Igor A.}, year={2019}, month={Jun} }
 @article{fang_cambareri_brown_feng_gouws_li_bolotnov_2018, title={Direct numerical simulation of reactor two-phase flows enabled by high-performance computing}, volume={330}, ISSN={["1872-759X"]}, DOI={10.1016/j.nucengdes.2018.02.024}, abstractNote={Nuclear reactor two-phase flows remain a great engineering challenge, where the high-resolution two-phase flow database which can inform practical model development is still sparse due to the extreme reactor operation conditions and measurement difficulties. Owing to the rapid growth of computing power, the direct numerical simulation (DNS) is enjoying a renewed interest in investigating the related flow problems. A combination between DNS and an interface tracking method can provide a unique opportunity to study two-phase flows based on first principles calculations. More importantly, state-of-the-art high-performance computing (HPC) facilities are helping unlock this great potential. This paper reviews the recent research progress of two-phase flow DNS related to reactor applications. The progress in large-scale bubbly flow DNS has been focused not only on the sheer size of those simulations in terms of resolved Reynolds number, but also on the associated advanced modeling and analysis techniques. Specifically, the current areas of active research include modeling of subcooled boiling, bubble coalescence, as well as the advanced post-processing toolkit for bubbly flow simulations in reactor geometries. A novel bubble tracking method has been developed to track the evolution of bubbles in two-phase bubbly flow. Also, spectral analysis of DNS database in different geometries has been performed to investigate the modulation of the energy spectrum slope due to bubble-induced turbulence. In addition, the single- and two-phase analysis results are presented for turbulent flows within the pressurized water reactor (PWR) core geometries. The related simulations are possible to carry out only with the world leading HPC platforms. These simulations are allowing more complex turbulence model development and validation for use in 3D multiphase computational fluid dynamics (M-CFD) codes.}, journal={NUCLEAR ENGINEERING AND DESIGN}, author={Fang, Jun and Cambareri, Joseph J. and Brown, Cameron S. and Feng, Jinyong and Gouws, Andre and Li, Mengnan and Bolotnov, Igor A.}, year={2018}, month={Apr}, pages={409–419} }
 @inproceedings{li_bolotnov_2016, title={Interface tracking simulation of phase-change phenomena: boiling and condensation verification}, DOI={10.1115/fedsm2016-7701}, abstractNote={Interface tracking simulation (ITS) is one of the promising approaches to describe heat transfer of boiling phenomena and their underlying mechanisms. Better understanding and modeling of this process will benefit various engineering systems. In modern nuclear reactors, study on nucleate boiling phenomena is very important for the prediction of the Critical Heat Flux (CHF) phenomena. The presented research will implement and verify the capability of evaporation process modeling by the massively parallel research code, PHASTA. The comparison of the numerical results and the analytical results demonstrates that the overall behavior of the simulation compares well with the analytical solution. A second simulation of the single bubble growth with non-uniform temperature distribution demonstrates both condensation and evaporation modeling. In the third simulation flow boiling capabilities were preliminary tested with laminar flow demonstration case. These results will be applied to a larger scale, multi-bubble simulations and help modeling of nucleate boiling phenomena.}, booktitle={Proceedings of the asme fluids engineering division summer meeting, 2016, vol 1a}, author={Li, M. N. and Bolotnov, Igor}, year={2016} }
 @article{kim_michielsen_2016, title={Synthesis of Antifungal Agents from Xanthene and Thiazine Dyes and Analysis of Their Effects}, volume={6}, ISSN={["2079-4991"]}, url={https://doi.org/10.3390/nano6120243}, DOI={10.3390/nano6120243}, abstractNote={Indoor fungi growth is an increasing home health problem as our homes are more tightly sealed. One thing that limits durability of the antifungal agents is the scarcity of reactive sites on many surfaces to attach these agents. In order to increase graft yield of photosensitizers to the fabrics, poly(acrylic acid-co-styrene sulfonic acid-co-vinyl benzyl rose bengal or phloxine B) were polymerized and then grafted to electrospun fabrics. In an alternative process, azure A or toluidine blue O were grafted to poly(acrylic acid), which was subsequently grafted to nanofiber-based and microfiber-based fabrics. The fabrics grafted with photosensitizers induced antifungal effects on all seven types of fungi in the order of rose bengal > phloxine B > toluidine blue O > azure A, which follows the quantum yield production of singlet oxygen for these photoactive dyes. Their inhibition rates for inactivating fungal spores decreased in the order of P. cinnamomi, T. viride, A. niger, A. fumigatus, C. globosum, P. funiculosum, and M. grisea, which is associated with lipid composition in membrane and the morphology of fungal spores. The antifungal activity was also correlated with the surface area of fabric types which grafted the photosensitizer covalently on the surface as determined by the bound color strength.}, number={12}, journal={NANOMATERIALS}, publisher={MDPI AG}, author={Kim, Joo Ran and Michielsen, Stephen}, year={2016}, month={Dec} }