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Numerical study of the effect of stenosis on the hemodynamics of a popliteal artery

AIP ADVANCES 2025年第2期15卷

作者： Shi, Liuliu Xiang, Xinru Liu, Jinlong Zhu, Wei Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China Shanghai Jiao Tong Univ Inst Pediat Translat Med Shanghai Childrens Med Ctr Sch Med Shanghai 200127 Peoples R China Shanghai Jiao Tong Univ Shanghai Engn Res Ctr Virtual Real Struct Heart Di Shanghai Childrens Med Ctr Sch Med Shanghai 200127 Peoples R China Shanghai Jiao Tong Univ Shanghai Inst Pediat Congenital Heart Dis Shanghai Childrens Med Ctr Sch Med Shanghai 200127 Peoples R China Guangdong Prov Hosp Chinese Med Dept Cardiothorac Surg Guangzhou 510006 Peoples R China Guangzhou Univ Chinese Med Affiliated Hosp 2 Guangzhou 510405 Peoples R China

The investigation of flow characteristics within the popliteal artery is fundamental to understanding the progression of lower limb arterial disease, given its high susceptibility to atherosclerosis and its frequent manifestation of stenosis. Research on the hemodynamics associated with popliteal artery stenosis remains limited, particularly in cardiovascular diseases. This study comprehensively examines how Newtonian and non-Newtonian fluid models influence the hemodynamic simulations of popliteal artery stenosis. key hemodynamic parameters, such as velocity, time-averaged wall shear stress (TAWSS), oscillatory shear index (OSI), and relative residence time (RRT), were systematically examined through numerical simulations to assess their influence and variability in arteries exhibiting different degrees of stenosis compared to healthy arteries. The findings indicate that both models' velocity and wall shear stress (WSS) distributions are largely comparable during the systolic phase (0.04-0.07 s), characterized by elevated velocities. However, during the countercurrent diastolic phase (0.21-0.40 s), the viscosity of the non-Newtonian fluid model experiences an increase, leading to reduced velocity distributions relative to the Newtonian fluid model. In particular, a 12% disparity in velocities is observed between the two models, indicating that the non-Newtonian model is better suited for comprehensive hemodynamic analysis in simulations involving stenotic popliteal arteries. Furthermore, a distinct flow separation occurs at the stenosis site, with blood flow velocity and WSS exhibiting significant increases as the stenosis severity escalates. For instances where hemodynamic parameters demonstrate minimal variations at stenosis levels below 60%, OSI and RRT are elevated. In contrast, TAWSS remains low, potentially fostering plaque formation. In contrast, when hemodynamic parameters undergo substantial changes at stenosis levels exceeding 60%, TAWSS rises, which may

关键词： Shear stress

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Quantitative description of self-, Maxwell-Stefan, and Fick diffusion coefficients in sucrose and citric acid solution based on molecular dynamics simulations

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PHYSICS OF FLUIDS 2025年第5期37卷

作者： Bao, Han Zhang, Chao Pan, Silin Zhang, Zhichao Yang, Yang Li, Shaopeng Wang, Yueshe Wiedensohler, Alfred Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Univ Shanghai Sci & Technol Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China Shanghai Marine Diesel Engine Res Inst Shanghai 201100 Peoples R China Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China Leibniz Inst Tropospher Res D-04318 Leipzig Germany

The diffusion coefficient plays a crucial role in predicting the equilibration timescale of atmospheric aerosol particles, however current knowledge on the subject remains limited. In this study, the self-, Maxwell-Stefan, and Fick diffusion coefficients in sucrose (SC) and citric acid (CA) solution are investigated using the molecular dynamics (MD) method. key aspects include comparisons with experimental and theoretical models, as well as the effects of temperature and solute concentration on diffusion coefficients. The results demonstrate that MD results align well with experimental data. Additionally, the McCarty-Mason equation and the Darken equation generally underpredict the self- and Maxwell-Stefan diffusion coefficients, respectively. The self-, Maxwell-Stefan, and Fick diffusion coefficients in SC and CA solutions exhibit a positive correlation with temperature and a negative correlation with solute mass fraction. Furthermore, the intensity of these influences varies: the impact of solute mass fraction on diffusion coefficients decreases with increasing temperature, while the effect of temperature diminishes with higher solute concentrations. Moreover, based on the MD simulation results, fitting formulas for the diffusion coefficients are also developed. This study underscores the value of the MD simulation method in accurately describing diffusion coefficients in solutions containing complex components.

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Experimental and numerical study on scroll compressor under different profile correction and discharge ports shapes

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INTERNATIONAL JOURNAL OF REFRIGERATION 2025年 169卷 241-253页

作者： Li, Kang Li, Chunyu Mohtaram, Soheil Liu, Ni Zhang, Hua Dou, Binlin Li, Chao He, Qize Abul Hasan, Mohd Islam, Saiful Wang, Jingwu Wang, Zilong Chen, Jianhong Aryanfar, Yashar Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Univ Shanghai Sci & Technol Key Lab Multiphase Flow & Heat Transfer Shanghai P Shanghai 200093 Peoples R China Invest Design & Res Inst Co Ltd Shanghai 200080 Peoples R China Shanghai Fire Res Inst MEM Shanghai 200032 Peoples R China King Khalid Univ Coll Engn Civil Engn Dept Abha 61421 Saudi Arabia Tsinghua Univ Hefei Inst Publ Safety Res Hefei 230601 Peoples R China Shanghai Yuanliu New Energy Technol Co Ltd Shanghai Peoples R China Hohai Univ Natl Key Lab Water Disaster Prevent Nanjing 211100 Jiangsu Peoples R China Autonomous Univ Ciudad Juarez Dept Elect Engn & Comp Sci Ciudad Juarez 32310 Mexico Khazar Univ Dept Mech Engn Thermo Fluids Res Grp Baku AZ Azerbaijan

The scroll compressor is an essential component in air conditioning and heat pump systems. This study examined an electric scroll compressor using R22 refrigerant, focusing on how modifications in the scroll head profile and discharge structure affect its performance. Initially, a semi-empirical model based on mathematical formulas was developed to predict the performance improvements of the updated scroll compressor. Three-dimensional simulation software was then used to illustrate changes in the internal flow dynamics before and after enhancements. The predictions were validated through experimental testing. Both the semi-empirical model and the three-dimensional unsteady numerical calculation model analyzed the effects of modifications to the tooth head profile and discharge port shape on compressor performance. The adoption of a PMP profile correction delayed the compressor discharge process, shifting the starting discharge angle from 315 degrees to 344 degrees, thereby reducing under-compression occurrences during operation and increasing volumetric efficiency by 1.31%. Additionally, mathematical formulas correlating temperature with compressor performance were developed from fitting data, predicting compressor behavior under various conditions. Moreover, replacing a circular discharge port with a waist-shaped port reduced power consumption by 0.59 kW, resulting in a more uniform temperature distribution and enhanced mass flow rate during compressor operation.

关键词： Electric scroll compressor Complete meshing profiles Discharge port shapes Compressor model flow field

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flow regime shift and temperature model of the radiation-induced convection system under surface cooling

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PHYSICS OF FLUIDS 2025年第3期37卷

作者： Zhou, Rui-Rui Yang, An-Wen You, Xiao-Gang Liu, Yun Sun, Ya-Song Li, Ling Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China Northwestern Polytech Univ Sch Power & Energy Shaanxi Key Lab Thermal Sci Aeroengine Syst Xian 710072 Peoples R China Changan Univ Sch Energy & Elect Engn Shaanxi Key Lab New Transportat Energy & Automot E Xian 710018 Peoples R China

The natural convection flow in the translucent fluid layer subjected to solar radiation heating plays a crucial role in the daytime heat and mass transfer in water bodies and solar energy collection. In a radiation-induced convection system under surface cooling, there are two possible flow regimes: the triple-layer and single-layer regimes. The flow regimes have a great influence on the mixing of fluid. The fluid is thermally stratified in the triple-layer regime, which should be avoided in the volumetric solar collector. In this paper, the transition condition of the flow regime shift between the triple-layer regime and the well-mixed single-layer regime is deduced since the thicknesses of the top and bottom mixing layers can be predicted through energy conservation analysis. Furthermore, a scaling analysis is conducted to obtain the scaling laws for the temperature differences across the thermal boundary layers regarding the control parameters, i.e., the Rayleigh number Ra, the Prandtl number Pr, the non-dimensional surface cooling heat flux phi, and the non-dimensional fluid depth H. A series of direct numerical simulations with the parameters in the range of 10(7) <= Ra <= 10(10), 0.7 <= Pr <= 70, 0 <= phi <= 0.7, and 0.5 <= H <= 3 are carried out to quantify the prefactor of scaling laws and also to validate the transition condition of the flow regime-shift. Then, a one-dimensional model can be developed to predict the temperature profile over the fluid depth with arbitrarily specified parameters. Thanks to the advantage of rapid and accurate prediction, this temperature model has a potential application for the design of the volumetric solar collector.

关键词： Prandtl number

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Numerical and experimental research of the characteristics of concentration solar cells

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Frontiers in Energy 2021年第2期15卷 279-291页

作者： Zilong WANG Hua ZHANG Binlin DOU Weidong WU Guanhua ZHANG Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering School of Energy and Power EngineeringUniversity of Shanghai for Science and TechnologyShanghai 200093China

The development of automatic tracking solar concentrator photovoltaic systems is currently attracting growing *** concentration photovoltaic systems(HCPVs)combining triple-junction InGaP/lnGaAs/Ge solar cells with a concentrator provide high conversion *** mathematical model for triple-junction solar cells,having a higher efficiency and superior temperature characteristics,was established based on the one-diode equivalent circuit cell model.A paraboloidal concentrator with a secondary optic system and a concentration ratio in the range of 100X–150X along with a sun tracking system was developed in this *** GaInP/GalnAs/Ge triple-junction solar cell,produced by AZUR SPACE Solar power,was also used in this *** solar cells produced by shanghai Solar Youth Energy(SY)and Shenzhen Yinshengsheng Technology ***.(YXS)were used as comparison samples in a further comparative study at different concentration ratios(200X–1000X).A detailed analysis on the factors that influence the electrical output characteristics of the InGaP/lnGaAs/Ge solar cell was conducted with a dish-style concentrating photovoltaic *** results show that the short-circuit current(Isc)and the open-circuit voltage(Voc)of multi-junction solar cells increases with the increasing concentration ratio,while the cell efficiency(ηc)of the solar cells increases first and then decreases with increasing concentration *** increasing solar cell temperature,Isc increases,while Voc andηc decrease.A comparison of the experimental and simulation results indicate that the maximum root mean square error is less than 10%,which provides a certain theoretical basis for the study of the characteristics of triple-junction solar cell that can be applied in the analysis and discussion regarding the influence of the relevant parameters on the performance of high concentration photovoltaic systems.

关键词： concentration three-junction solar cell mathematical model electrical properties solar energy

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Study on Liutex-driven reward for intelligent flow control by dynamic feature-based deep reinforcement learning

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AIP Advances 2025年第5期15卷

作者： Wang, Qi Dong, Xiangrui You, Sunyu Cai, Xiaoshu School of Energy and Power Engineering University of Shanghai for Science and Technology Shanghai200093 China Shanghai Key Laboratory of Multiphase Flow and Heat Transfer for Power Engineering Shanghai200093 China

The issue of flow separation over an airfoil under weak turbulent conditions is addressed and resolved through the deep reinforcement learning (DRL) strategy. To suppress the generation of separation flow and the instability of the vortex shedding alley over an airfoil, a novel reward function named RLiutex, considering the suppression of the rigid rotation intensity and core size of the vortex, is first proposed in this paper. The great potential of this Liutex-driven reward for effective large eddy elimination and aerodynamic optimization is verified in this work. Furthermore, a dynamic feature-based DRL (DF-DRL) framework is redeveloped to markedly enhance the learning efficiency and convergence speed. The combination of the Liutex-driven reward function with the DF-DRL framework results in an exceptional aerodynamic performance, with minimal fluctuations in both drag and lift coefficients, highlighting the potential of this approach for advanced flow control strategies. © 2025 Author(s).

关键词： Deep reinforcement learning

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Numerical simulation of flow characteristics for a labyrinth passage in a pressure valve

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Journal of Hydrodynamics 2016年第4期28卷 629-636页

作者：王海民赵越汪建兴孔祥帅刘欢李科良王喜芳 School of Energy and Power Engineering University of Shanghai for Science and Technology Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering University of Shanghai for Science and Technology

A tortuous labyrinth passage consists of a series of right angle turns in a disk of high pressure control *** this paper,numerical simulations are made for the velocity and pressure distributions in this *** is shown that the “series passage” can induce a pressure dropping more *** main function of the “series passage” is to induce a pressure dropping while the “parallel passage” is mainly to regulate the *** a cross sectional area process,a series of reduction and expansion,the pressure will also see dropping and partial recovery,which is called the multistage pressure *** this way,the velocity can be controlled in a reasonable level anywhere in this tortuous labyrinth *** the fluid pressure dropping in a downwards serrated way,the pressure is higher than the local saturate vapor pressure,therefore,no cavitation is induced by the phase transition.

关键词： passage valve dropping multistage turns sectional anywhere regulate vortex inlet

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Modeling and prediction of ultrasonic attenuations in liquid-solid dispersions containing mixed particles with Monte Carlo method

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Particuology 2019年第2期17卷 84-91页

作者： Jianfei Gu Fengxian Fan Yunsi Li Huinan Yang Mingxu Su Xiaoshu Cai Institute of Particle and Two-Phase Flow Measurement/Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering University of Shanghai for Science and Technology Shanghai 200093 China

We develop a theoretical model for predicting the ultrasonic attenuation in the liquid-solid system containing mixed particles. The ultrasonic attenuation coefficient is obtained by counting the number of phonons that reach the receiver. Using the Monte Carlo method (MCM), numerical simulations were performed to predict the ultrasonic attenuations with not only a single particle type but also monodisperse and polydisperse mixed particles. The simulation results for the systems with a single particle type were compared with various standard models. The results show that they agree well at relatively low particle volume concentrations (within 10%). For systems with mixed particles, the particle volume concentrati on was found to in crease to around 10%, and the variation of the ultrasonic attenuation agai nst the mixing ratio yields a nonlinear trend. Moreover, the ultrasonic attenuation is significantly affected by particle properties. The numerical results also show that both the particle type and particle size distribution should be carefully taken into account in the dispersions with polydisperse mixed particles, where the MCM can give a more direct description of the physics of sound propagation compared with the conventional models.

关键词： Ultrasound Ultrasonic attenuation Monte Carlo method Particle size measurement

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Experimental study on dynamic mechanism of vortex evolution in a turbulent boundary layer of low Reynolds number

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Journal of Hydrodynamics 2020年第5期32卷 807-819页

作者： Yan-ang Guo Xiang-rui Dong Xiao-shu Cai Wu Zhou School of Energy and Power Engineering University of Shanghai for Science and TechnologyShanghai 200093China Key Laboratory of Multiphase Flow and Heat Transfer in Shanghai Power Engineering Shanghai 200093China

The dynamic mechanism of the vortex generation and evolution process in a fully developed turbulent boundary layer with Reθ=97-194 is experimentally *** this study,a moving single-frame and long-exposure(MSFLE)imaging method and a moving particle image velocimetry/particle tracing velocimetry(M-PIV/PTV)are designed and implemented for measuring the temporal and spatial evolution of vortex cores in both qualitative and quantitative ways,*** the other hand,the Liutex vector,which is a new mathematical definition and identification of the vortex core proposed by Liu’s group,is first applied in the experiment for the structural visualization and quantitative analysis of the local fluid *** results show that an intuitional process of vortex evolution can be clearly observed by tracking the vortex using MSFLE and verify that the roll-up of the shear layer induced by shear instability is the origin of vortex formation in ***,a quantitative investigation in terms of the critical vortex core boundary(size)and its accurate rotation strength is carried out based on the Liutex vector field analysis by M-PIV/*** to statistics of the relation between vortex core size and the rotation strength during the whole process,the physical mechanism of vortex generation and evolution in a turbulent boundary layer of low Reynolds number can be summarized as a four-dominant-state course consisting of the“synchronous linear segment(SL)-absolute enhancement segment(AE)-absolute diffusion segment(AD)-skewing dissipation segment(SD)”.

关键词： Turbulent boundary layer high-and low-speed fluid vortex generation moving single-frame and long-exposure moving particle image velocimetry/particle tracing velocimetry Liutex vector

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Influence of Soil-Structure Interaction Models on the Dynamic Responses of An Offshore Wind Turbine Under Environmental Loads

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China Ocean engineering 2023年第2期37卷 218-231页

作者： TANG Hong-ming YUE Min-nan YAN Yang-tian LI Zhi-hao LI Chun NIU Kai-lun School of Energy and Power Engineering University of Shanghai for Science and TechnologyShanghai 200093China Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering Shanghai 200093China

Offshore wind turbines(OWTs) suffer wind, wave and earthquake loads. The investigation of OWTs' dynamic response under environmental loads is essential for structural safety assessment. The soil-structure interaction(SSI)significantly affects the responses of OWT under environmental loads. However, there is few systematic research about the difference in the dynamic response of different SSI models under environmental loads. In order to solve the problem, the OWT is modeled by shell element, and several SSI models are built. The wind, wave and earthquake loads are taken into account. Moreover, the dynamic response, fatigue and buckling analysis are performed by ANSYS. The results indicate that SSI cannot be ignored in the dynamic response of the OWT under wind and wave loads. The SSI can decrease the displacement response of the OWT by 19% under wind and wave loads and reduce the fatigue damage of the pile. Multi-layer SSI can strongly influence the OWT's dynamic response under wind and wave loads or earthquake-only load. The vertical earthquake load increases the dynamic response in three ***, in order to simulate real environment, multi-layer SSI, soil damping and vertical SSI must be considered to evaluate the displacement response of the OWT under wind, wave and earthquake loads. The earthquake and gravity loads can cause more obvious response of the OWT than that of only wind and wave loads. The top and bottom of the tower are prone to occur buckling.

关键词： OWT soil structure interaction earthquake dynamic analysis structural damage

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