本研究旨在模拟不同狭窄程度和脉搏率的颈动脉搏动血流。采用流-固耦合(FSI)和任意拉格朗日-欧拉(ALE)方法研究了不同狭窄程度、脉搏率和动脉壁性质对周围流体的影响。分别应用Carreau-Yasuda非牛顿超弹性模型和修正Mooney-Rivin超弹性...本研究旨在模拟不同狭窄程度和脉搏率的颈动脉搏动血流。采用流-固耦合(FSI)和任意拉格朗日-欧拉(ALE)方法研究了不同狭窄程度、脉搏率和动脉壁性质对周围流体的影响。分别应用Carreau-Yasuda非牛顿超弹性模型和修正Mooney-Rivin超弹性模型于具有非牛顿行为的血液和超弹性血管壁。结果得到血液的壁面径向位移、压力分布、轴向速度分布和壁面剪切应力。通过增加狭窄的严重程度,轴向速度、血压变化、最大壁面剪切应力和壁面径向位移均呈增长趋势。当脉率在狭窄程度为75%时,最大流量矩、壁面径向位移、压力、轴向速度和壁面剪应力的最大值均增大。此外,与弹性和刚性模型相比,将动脉壁视为超弹性模型,将其周围流体视为非牛顿和非定常,可以使模拟更加真实。在严重程度高达50%的狭窄中,红细胞受到轻微损害,而在严重程度为75%的狭窄中观察到溶血。通过改善动脉粥样硬化,弹性模量从500 k Pa提高到2 MPa,在60 bpm脉率和狭窄程度75%下,剪切应力最大值增长65%。与刚性和弹性动脉壁相比,动脉壁的超弹性模型导致较低的轴向速度、较低的血压、较低的剪切应力和较高的径向位移。展开更多
Heat transfer and entropy generation of developing laminar forced convection flow of water-Al_2O_3 nanofluid in a concentric annulus with constant heat flux on the walls is investigated numerically. In order to determ...Heat transfer and entropy generation of developing laminar forced convection flow of water-Al_2O_3 nanofluid in a concentric annulus with constant heat flux on the walls is investigated numerically. In order to determine entropy generation of fully developed flow, two approaches are employed and it is shown that only one of these methods can provide appropriate results for flow inside annuli. The effects of concentration of nanoparticles, Reynolds number and thermal boundaries on heat transfer enhancement and entropy generation of developing laminar flow inside annuli with different radius ratios and same cross sectional areas are studied. The results show that radius ratio is a very important decision parameter of an annular heat exchanger such that in each Re, there is an optimum radius ratio to maximize Nu and minimize entropy generation. Moreover, the effect of nanoparticles concentration on heat transfer enhancement and minimizing entropy generation is stronger at higher Reynolds.展开更多
Authors’ first and last names were interchanged in the original version of the article and they should be replaced as follows: Majid Siavashi, Mohammad Jamali.
Streamline simulation is developed to simulate waterflooding in fractured reservoirs. Conventional reservoir simulation methods for fluid flow simulation in large and complex reservoirs are very costly and time consum...Streamline simulation is developed to simulate waterflooding in fractured reservoirs. Conventional reservoir simulation methods for fluid flow simulation in large and complex reservoirs are very costly and time consuming. In streamline method, transport equations are solved on one-dimensional streamlines to reduce the computation time with less memory for simulation. First, pressure equation is solved on an Eulerian grid and streamlines are traced. Defining the "time of flight", saturation equations are mapped and solved on streamlines. Finally, the results are mapped back on Eulerian grid and the process is repeated until the simulation end time. The waterflooding process is considered in a fractured reservoir using the dual porosity model. Afterwards, a computational code is developed to solve the same problem by the IMPES method and the results of streamline simulation are compared to those of the IMPES and a commercial software. Finally, the accuracy and efficiency of streamline simulator for simulation of two-phase flow in fractured reservoirs has been proved.展开更多
Proton Exchange Membrane Fuel Cells(PEMFCs)are known as a promising alternative for internal combustion engines(ICE)to reduce pollution.Recent progress of PEMFCs is heading towards achieving higher power densities,red...Proton Exchange Membrane Fuel Cells(PEMFCs)are known as a promising alternative for internal combustion engines(ICE)to reduce pollution.Recent progress of PEMFCs is heading towards achieving higher power densities,reducing the refueling time,and decreasing the degradations,to facilitate the commercialization of hydrogen mobility.Model-assisted stack component development,diagnosis,and management are essential to ensure improved stack design and operation for tackling the existing implementation challenges of PEMFCs.Past reviews usually touched on a specific aspect,which can hardly provide the readers a complete picture of the key challenges and advances in water management.This paper aims at delivering a comprehensive source to review,from both experimental,analytical,and numerical viewpoints,the key operational challenges,and solutions of the stack to improve water/thermal management and cold start.In addition to presenting the fundamental theory to develop an analytical model,the recent advances in the flow field design,nanofluid coolants,and cold-start methods.Furthermore,the impacts of microstructural properties and the design of the porous layers on the water/thermal management are described.展开更多
文摘本研究旨在模拟不同狭窄程度和脉搏率的颈动脉搏动血流。采用流-固耦合(FSI)和任意拉格朗日-欧拉(ALE)方法研究了不同狭窄程度、脉搏率和动脉壁性质对周围流体的影响。分别应用Carreau-Yasuda非牛顿超弹性模型和修正Mooney-Rivin超弹性模型于具有非牛顿行为的血液和超弹性血管壁。结果得到血液的壁面径向位移、压力分布、轴向速度分布和壁面剪切应力。通过增加狭窄的严重程度,轴向速度、血压变化、最大壁面剪切应力和壁面径向位移均呈增长趋势。当脉率在狭窄程度为75%时,最大流量矩、壁面径向位移、压力、轴向速度和壁面剪应力的最大值均增大。此外,与弹性和刚性模型相比,将动脉壁视为超弹性模型,将其周围流体视为非牛顿和非定常,可以使模拟更加真实。在严重程度高达50%的狭窄中,红细胞受到轻微损害,而在严重程度为75%的狭窄中观察到溶血。通过改善动脉粥样硬化,弹性模量从500 k Pa提高到2 MPa,在60 bpm脉率和狭窄程度75%下,剪切应力最大值增长65%。与刚性和弹性动脉壁相比,动脉壁的超弹性模型导致较低的轴向速度、较低的血压、较低的剪切应力和较高的径向位移。
文摘Heat transfer and entropy generation of developing laminar forced convection flow of water-Al_2O_3 nanofluid in a concentric annulus with constant heat flux on the walls is investigated numerically. In order to determine entropy generation of fully developed flow, two approaches are employed and it is shown that only one of these methods can provide appropriate results for flow inside annuli. The effects of concentration of nanoparticles, Reynolds number and thermal boundaries on heat transfer enhancement and entropy generation of developing laminar flow inside annuli with different radius ratios and same cross sectional areas are studied. The results show that radius ratio is a very important decision parameter of an annular heat exchanger such that in each Re, there is an optimum radius ratio to maximize Nu and minimize entropy generation. Moreover, the effect of nanoparticles concentration on heat transfer enhancement and minimizing entropy generation is stronger at higher Reynolds.
文摘Authors’ first and last names were interchanged in the original version of the article and they should be replaced as follows: Majid Siavashi, Mohammad Jamali.
文摘Streamline simulation is developed to simulate waterflooding in fractured reservoirs. Conventional reservoir simulation methods for fluid flow simulation in large and complex reservoirs are very costly and time consuming. In streamline method, transport equations are solved on one-dimensional streamlines to reduce the computation time with less memory for simulation. First, pressure equation is solved on an Eulerian grid and streamlines are traced. Defining the "time of flight", saturation equations are mapped and solved on streamlines. Finally, the results are mapped back on Eulerian grid and the process is repeated until the simulation end time. The waterflooding process is considered in a fractured reservoir using the dual porosity model. Afterwards, a computational code is developed to solve the same problem by the IMPES method and the results of streamline simulation are compared to those of the IMPES and a commercial software. Finally, the accuracy and efficiency of streamline simulator for simulation of two-phase flow in fractured reservoirs has been proved.
基金the European Union’s Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement No.754354.
文摘Proton Exchange Membrane Fuel Cells(PEMFCs)are known as a promising alternative for internal combustion engines(ICE)to reduce pollution.Recent progress of PEMFCs is heading towards achieving higher power densities,reducing the refueling time,and decreasing the degradations,to facilitate the commercialization of hydrogen mobility.Model-assisted stack component development,diagnosis,and management are essential to ensure improved stack design and operation for tackling the existing implementation challenges of PEMFCs.Past reviews usually touched on a specific aspect,which can hardly provide the readers a complete picture of the key challenges and advances in water management.This paper aims at delivering a comprehensive source to review,from both experimental,analytical,and numerical viewpoints,the key operational challenges,and solutions of the stack to improve water/thermal management and cold start.In addition to presenting the fundamental theory to develop an analytical model,the recent advances in the flow field design,nanofluid coolants,and cold-start methods.Furthermore,the impacts of microstructural properties and the design of the porous layers on the water/thermal management are described.
