The macro modeling and the solution of traffic flow with road width were investigated.Firstly,a new macro model with the consideration of road width was proposed.Secondly,the effects of road width on uniform flow and ...The macro modeling and the solution of traffic flow with road width were investigated.Firstly,a new macro model with the consideration of road width was proposed.Secondly,the effects of road width on uniform flow and small perturbation were studied.The analytical and numerical results show that widening (shrinking) road can enhance (reduce) the equilibrium speed and flow,and the increments (decrements) will increase with the absolute value of road width gradient.In addition,the numerical results illustrate that the new model can describe the effects of road width on the evolutions of uniform flow and small perturbation.展开更多
The method of numerical simulation was applied to investigate the effects of jet impinging plate thickness and its thermal conductivity on the local heat flux distribution along the impinging plate. The results show t...The method of numerical simulation was applied to investigate the effects of jet impinging plate thickness and its thermal conductivity on the local heat flux distribution along the impinging plate. The results show that the two factors have great effects on the heat flux distribution. The non-uniformity of the local heat-flux on the impinging plate surface gets more profound as the plate becomes thicker and thermal conductivity gets larger. When Reynolds number is 5000, the ratio of nozzle-to-plate spacing to nozzle diameter is 5 and thermal conductivity is 16W/(m·K), and even for the plate with only 25μm in thickness, the non-uniformity of the heat flux cannot be neglected. When the plate thickness is 50 μm, only when thermal conductivity is as small as 1W/(m·K), the heat flux curve can be approximately treated as an iso-heat-flux boundary. In the experimental research, a real non-iso-heat-flux boundary is treated as an iso-heat-flux boundary, which would result in under-estimated Nusselt number value in the stagnation zone and an over-estimated value outside. Such an experimental Nusselt number distribution is taken to evaluate turbulent model, and the conclusion would be drawn that the turbulent model over-predicts the stagnation heat transfer. This is one of the important reasons why many literatures reported that k-ε turbulent model dramatically over-predicts the impinging jet heat transfer in the stagnation region.展开更多
This study is concerned with the numerical simulation of the flow through an open type cross-flow runner of a nano-hydraulic turbine driven by rapid and shallow stream. It employs the two-dimensional particle method, ...This study is concerned with the numerical simulation of the flow through an open type cross-flow runner of a nano-hydraulic turbine driven by rapid and shallow stream. It employs the two-dimensional particle method, which was used for the flow simulation of a small-scale hydraulic turbine of impulse-type in the prior study. The tip speed ratio 2, defined as the ratio of the runner tip speed to the water stream velocity upstream of the runner, ranges from 0.1 to 0.8. The simulated flow at 2 = 0.5 is confirmed to agree well with the experimentally visualized one. The effect of 2 on the flows inside the rotating cascade as well as around the runner is clarified. The turbine performance, calculated by using the simulated flow, is also highlighted to agree almost with the measurement. These demonstrate that the present simulation method is indeed applicable to the development of open type cross-flow runner of nano-hydraulic turbine utilizing rapid and shallow stream.展开更多
Immiscible kerosene-water two-phase flows in microchannels connected by a T-junction were numerically studied by a Lattice Boltzmann (LB) method based on field mediators.The two-phase flow lattice Boltzmann model was ...Immiscible kerosene-water two-phase flows in microchannels connected by a T-junction were numerically studied by a Lattice Boltzmann (LB) method based on field mediators.The two-phase flow lattice Boltzmann model was first validated and improved by several test cases of a still droplet.The five distinct flow regimes of the kerosene-water system,previously identified in the experiments from Zhao et al.,were reproduced.The quantitative and qualitative agreement between the simulations and the experimental data show the effectiveness of the numerical method.The roles of the interfacial tension and contact angle on the flow patterns and shapes of droplets were discussed and highlighted according to the numerical results based on the improved two-phase LB model.This work demonstrated that the developed LBM simulator is a viable tool to study immiscible two-phase flows in microchannels,and such a tool could provide tangible guidance for the design of various microfluidic devices that involve immiscible multi-phase flows.展开更多
基金Supported by the National Natural Science Foundation of China(11761054,11261035,11571002)the Program for Young Talents of Science and Technology in Universities of Inner Mongolia Autonomous Region(NJYT-15-A07)+3 种基金the Natural Science Foundation of Inner Mongolia Autonomous Region,China(2015MS0108,2012MS0102)the Science Research Foundation of Institute of Higher Education of Inner Mongolia Autonomous Region,China(NJZZ12198,NJZZ16234,NJZZ16235)Science and Technology Development Foundation of CAEP(2015B0101021)Defense Industrial Technology Development Program(B1520133015)
基金Project(NCET-08-0038) supported by the Program for New Century Excellent Talents in Chinese UniversityProjects(70701002,70971007 and 70521001) supported by the National Natural Science Foundation of ChinaProject(2006CB705503) supported by the National Basic Research Program of China
文摘The macro modeling and the solution of traffic flow with road width were investigated.Firstly,a new macro model with the consideration of road width was proposed.Secondly,the effects of road width on uniform flow and small perturbation were studied.The analytical and numerical results show that widening (shrinking) road can enhance (reduce) the equilibrium speed and flow,and the increments (decrements) will increase with the absolute value of road width gradient.In addition,the numerical results illustrate that the new model can describe the effects of road width on the evolutions of uniform flow and small perturbation.
基金Project(50376076) supported by the National Natural Science Foundation of China
文摘The method of numerical simulation was applied to investigate the effects of jet impinging plate thickness and its thermal conductivity on the local heat flux distribution along the impinging plate. The results show that the two factors have great effects on the heat flux distribution. The non-uniformity of the local heat-flux on the impinging plate surface gets more profound as the plate becomes thicker and thermal conductivity gets larger. When Reynolds number is 5000, the ratio of nozzle-to-plate spacing to nozzle diameter is 5 and thermal conductivity is 16W/(m·K), and even for the plate with only 25μm in thickness, the non-uniformity of the heat flux cannot be neglected. When the plate thickness is 50 μm, only when thermal conductivity is as small as 1W/(m·K), the heat flux curve can be approximately treated as an iso-heat-flux boundary. In the experimental research, a real non-iso-heat-flux boundary is treated as an iso-heat-flux boundary, which would result in under-estimated Nusselt number value in the stagnation zone and an over-estimated value outside. Such an experimental Nusselt number distribution is taken to evaluate turbulent model, and the conclusion would be drawn that the turbulent model over-predicts the stagnation heat transfer. This is one of the important reasons why many literatures reported that k-ε turbulent model dramatically over-predicts the impinging jet heat transfer in the stagnation region.
文摘This study is concerned with the numerical simulation of the flow through an open type cross-flow runner of a nano-hydraulic turbine driven by rapid and shallow stream. It employs the two-dimensional particle method, which was used for the flow simulation of a small-scale hydraulic turbine of impulse-type in the prior study. The tip speed ratio 2, defined as the ratio of the runner tip speed to the water stream velocity upstream of the runner, ranges from 0.1 to 0.8. The simulated flow at 2 = 0.5 is confirmed to agree well with the experimentally visualized one. The effect of 2 on the flows inside the rotating cascade as well as around the runner is clarified. The turbine performance, calculated by using the simulated flow, is also highlighted to agree almost with the measurement. These demonstrate that the present simulation method is indeed applicable to the development of open type cross-flow runner of nano-hydraulic turbine utilizing rapid and shallow stream.
基金supported by Corning Incorporated, the National Natural Science Foundation of China (20990224, 20976177)National Science Fund for Distinguished Young Scholars (21025627)the National Basic Research Program of China (2009CB623406)
文摘Immiscible kerosene-water two-phase flows in microchannels connected by a T-junction were numerically studied by a Lattice Boltzmann (LB) method based on field mediators.The two-phase flow lattice Boltzmann model was first validated and improved by several test cases of a still droplet.The five distinct flow regimes of the kerosene-water system,previously identified in the experiments from Zhao et al.,were reproduced.The quantitative and qualitative agreement between the simulations and the experimental data show the effectiveness of the numerical method.The roles of the interfacial tension and contact angle on the flow patterns and shapes of droplets were discussed and highlighted according to the numerical results based on the improved two-phase LB model.This work demonstrated that the developed LBM simulator is a viable tool to study immiscible two-phase flows in microchannels,and such a tool could provide tangible guidance for the design of various microfluidic devices that involve immiscible multi-phase flows.
