@article{zhou_qiu_wang_gao_liu_2018, title={Dynamic analysis of a planar multi-stage centrifugal pump rotor system based on a novel coupled model}, volume={434}, ISSN={["1095-8568"]}, DOI={10.1016/j.jsv.2018.07.041}, abstractNote={The coupled rotor-dynamics issue is always one of the most important and difficult research for multi-stage pump system due to the complexity of multiple fluid-induced forces and multi-degree of freedom rotor model. In this paper, the Reynolds equation of journal bearing is solved by the finite difference method and corresponding fluid-induced force is obtained by small parameter method. In addition, the dynamic coefficients of annular seal are calculated according to bulk-flow model and perturbation method. Furthermore, a novel rotor system model fully considering the coupled effects of bearing and seal is proposed by matrix manipulation method. Then the coupled rotor-dynamics for multi-stage pump system is investigated subsequently based on the novel model. Finally, the Lomakin effect of annular seal is studied in detail. The calculated results indicate that the fluid-induced force of seal exerting on the rotor system should not be ignored in the calculation of coupled dynamic characteristics. Smaller length and clearance of annular seal are good for the stability of coupled rotor system. Compared with asymmetric structure, the symmetric sealing structure has a larger stability margin on condition of ‘rigid rotor’ status. Moreover, the Lomakin effect on stability presents linear superposition property. The proposed method can provide valuable reference for the design and modeling of multi-dimensional matrix system.}, journal={JOURNAL OF SOUND AND VIBRATION}, author={Zhou, Wenjie and Qiu, Ning and Wang, Leqin and Gao, Bo and Liu, Dong}, year={2018}, month={Nov}, pages={237–260} }
 @article{ducoste_liu_linden_2005, title={Alternative approaches to modeling fluence distribution and microbial inactivation in ultraviolet reactors: Lagrangian versus Eulerian}, volume={131}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-26444592023&partnerID=MN8TOARS}, DOI={10.1061/(asce)0733-9372(2005)131:10(1393)}, abstractNote={A study was performed to evaluate alternative methods for predicting the ultraviolet (UV) reactor performance using computational fluid dynamics. The study consists of modeling the UV fluence distribution and microbial inactivation using either Lagrangian or Eulerian methods for both low- and medium-pressure UV reactors. In the Eulerian method, fluence distributions were calculated using a flow-weighted and a mass-weighted fraction technique. The results show that the Eulerian flow-weighted fraction fluence distribution agreed well with the Lagrangian particle tracking fluence distribution when applied to the UV reactor outlet plane. However, when applied to planes downstream from effluent hydraulic structures, the Eulerian fluence distribution method was influenced by the additional convective mixing from these hydraulic structures and predicts a tighter fluence distribution range than the Lagrangian method. The Eulerian approach to modeling microbial inactivation seems comparable to the Lagrangian particle tracking approach and can be viewed as a suitable alternative to the Lagrangian approach. The results also show that the Eulerian mass-weighted fraction distribution is comparable to the microbial kinetic weighted Lagrangian particle tracking approach, which can provide greater sensitivity to the low fluence regions in the UV reactor.}, number={10}, journal={Journal of Environmental Engineering (New York, N.Y.)}, author={Ducoste, J. and Liu, D. and Linden, K.}, year={2005}, pages={1393–1403} }
 @article{ducoste_linden_rokjer_liu_2005, title={Assessment of reduction equivalent fluence bias using computational fluid dynamics}, volume={22}, ISSN={["1557-9018"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-23944504236&partnerID=MN8TOARS}, DOI={10.1089/ees.2005.22.615}, abstractNote={A study was performed to investigate the use of computational fluid dynamics (CFD) coupled with a fluence rate model to determine the bias in UV biodosimetry measurements using inactivation of a challenge microbe instead of the target pathogen—termed the reduction equivalent fluence (REF) bias. Simulations were performed using two fluence rate models: RADial Line Source Integration (RADLSI), and UVCalc3D, a multiple segment source summation (MSSS). CFD UV models were carried out in several closed-conduit UV reactors using either mono- or polychromatic lamps. Simulations were also performed with different UV transmittances, flow rates, lamp power settings, and with lamps out of service. In addition, the Cryptosporidium fluence response kinetics was approximated using two nonlinear models: a P-factor model, and a Rational model. The REF bias was computed using the predicted fluence distribution from a Lagrangian particle tracking routine and compared with the REF bias computed using the EPA UV disinfection ...}, number={5}, journal={ENVIRONMENTAL ENGINEERING SCIENCE}, author={Ducoste, J and Linden, K and Rokjer, D and Liu, D}, year={2005}, pages={615–628} }
 @article{jin_linden_ducoste_liu_2005, title={Impact of lamp shadowing and reflection on the fluence rate distribution in a multiple low-pressure UV lamp array}, volume={39}, ISSN={["0043-1354"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-21744448033&partnerID=MN8TOARS}, DOI={10.1016/j.watres.2005.04.071}, abstractNote={Use of mathematical modeling for determination of ultraviolet (UV) fluence in disinfection reactors requires accurate knowledge of the fluence rate distribution in a multiple lamp array. A method for measuring the fluence rate among a multiple lamp array was demonstrated using spherical actinometry. A matrix of four low-pressure UV lamps in air were investigated to evaluate the potential for shadowing and reflection to impact the fluence rate within and surrounding the lamp array. Two fluence rate distribution models were tested to determine the ability to predict the fluence rate distribution measured by the actinometers. Shadowing proved to attenuate UV light. Reflection from the lamp surface added 3-9% to the fluence rate, depending upon position in the reactor. These effects, as well as the fluence rate at various points in the lamp matrix were effectively modeled using RAD-LSI and UVCalc3D fluence rate distribution models. At fluence rates above 8mWcm(-2), the actinometry measured fluence rate was lower than the modeled rate, presumably from saturation of the actinometer solution at high fluence rates (close to the lamp). With multiple lamp reactors, the impact of shadowing can significantly affect fluence rate distribution and thus the level of microbial inactivation. If shadowing is not included in fluence rate distribution models, the fluence rate will be over predicted in the shadow zone of a neighboring lamp, falsely skewing model inactivation predictions.}, number={12}, journal={WATER RESEARCH}, author={Jin, SS and Linden, KG and Ducoste, J and Liu, D}, year={2005}, month={Jul}, pages={2711–2721} }
 @article{liu_ducoste_jin_linden_2004, title={Evaluation of alternative fluence rate distribution models}, volume={53}, ISSN={["1365-2087"]}, DOI={10.2166/aqua.2004.0031}, abstractNote={A detailed evaluation of several fluence rate distribution models was performed. These models included line source integration (LSI), multiple points source summation (MPSS), multiple segment source summation (MSSS), UVCalc3D, RAD-LSI, view factor and discrete ordinate (DO). As part of the evaluation, a complete MSSS model, which accounts for the quartz sleeve thickness when calculating the refraction angles, was developed. In addition, a simple attenuation factor was introduced to integrate the physics of reflection, refraction and absorption effects into the LSI model. As an alternative simple correction to the LSI, the RAD-LSI incorporates the RADIAL intensity model into the original LSI formulation. All models were compared with experimental measurements using spherical actinometers, which measure the fluence rate at specific points in space. Experimental measurements were performed in air and water. Experiments in water were performed at two different ultraviolet transmittance (UVTs) (77 and 88%). The results showed that models that neglected the effects of refraction deviated significantly from the experimental data. In addition, the MSSS approach or models that incorporated the MSSS concept were found to best match the experimentally measured fluence rate distribution. Moreover, little difference was found between the results of MSSS with quartz sleeve thickness and UVCalc3D, which does not model the quartz sleeve thickness in the refraction angle calculation but uses a factor to account for the effects of the quartz sleeve on the fluence rate. The attenuation factor combined with the LSI model was found to match the MSSS model predictions, while reducing the computational cost.}, number={6}, journal={JOURNAL OF WATER SUPPLY RESEARCH AND TECHNOLOGY-AQUA}, author={Liu, D and Ducoste, J and Jin, S and Linden, K}, year={2004}, month={Sep}, pages={391–408} }