The influence of chemical nonequilibrium on the thermal characteristics is explored by using the 2Dhybrid grid direct simulation Monte Carlo(DSMC)parallel method.An improved molecule search algorithm is proposed,which...The influence of chemical nonequilibrium on the thermal characteristics is explored by using the 2Dhybrid grid direct simulation Monte Carlo(DSMC)parallel method.An improved molecule search algorithm is proposed,which can preserve the high efficiency of area search algorithm.This method can overcome the defects of area search algorithm,and give all information about molecules hitting surface.The heat flux calculation method for a rarefied hypersonic flow is established.In addition,the testing methods of chemical reaction probability for five species of mixed gas with limited speed chemical reactions are also selected.To validate the effectiveness of the present method,hypersonic flow around a cylinder is firstly simulated,and subsequently numerical simulations of the heat flux and flow field characteristics around the blunt body at different heights are carried out in two different cases:the thermal nonequilibrium condition and the thermochemical nonequilibrium condition.Numerical results demonstrate the validity and reliability of the proposed methods.展开更多
Using the process parameter description,we analyzed the difference between the characteristics of laminar convections through parallel plain planes with uniform temperature and heat flux.The results show the following...Using the process parameter description,we analyzed the difference between the characteristics of laminar convections through parallel plain planes with uniform temperature and heat flux.The results show the following.(1)On the wall surface of the developing region,under uniform heat flux boundary condition,the heat flux normal to the wall surface is transported through a convection process although the velocity is zero;the velocity gradient contributes to this transport,but under uniform temperature boundary condition,the heat flux normal to the wall surface is transported through a difussion process.(2)Inside the flow of the developing region,whether under uniform temperature or heat flux boundary condition,the heat flux along the main flow direction and the heat flux normal to the wall surface are transported through a convection process,and the contributions of velocity and velocity gradient are dependent on the thermal boundary condition.(3)On the wall surface of the fully developed region,under uniform heat flux boundary condition,the heat flux normal to the wall surface is transported through a convection process;the velocity gradient contributes to this transport,but under uniform temperature boundary condition,the heat flux normal to the wall surface is transported through a diffusion process.(4)Inside the flow of the fully developed region,under uniform temperature boundary condition,the heat flux along the main flow direction and the heat flux normal to the wall surface are transported through a convection process,and the velocity and velocity gradient contribute to these transports;under uniform heat flux boundary condition,the heat flux along the main flow direction and the heat flux normal to the wall surface are transported through a convection process.Furthermore,the transport of the heat flux along the main flow direction is a no-net convection process;the velocity gradient contributes to the transport of the heat flux only in the normal direction of the wall surface.(5)Simply because the maximum velocity gradient component on the wall surface contributes to the transport of the heat flux normal to the wall surface under uniform heat flux boundary condition,it does not contribute to this transport under uniform temperature boundary condition;thus,the heat transfer intensity under uniform heat flux boundary condition is stronger than that under uniform temperature boundary condition.展开更多
基金supported by the National Defense Basic Research Program during the Twelfth Five-Year Plan Period
文摘The influence of chemical nonequilibrium on the thermal characteristics is explored by using the 2Dhybrid grid direct simulation Monte Carlo(DSMC)parallel method.An improved molecule search algorithm is proposed,which can preserve the high efficiency of area search algorithm.This method can overcome the defects of area search algorithm,and give all information about molecules hitting surface.The heat flux calculation method for a rarefied hypersonic flow is established.In addition,the testing methods of chemical reaction probability for five species of mixed gas with limited speed chemical reactions are also selected.To validate the effectiveness of the present method,hypersonic flow around a cylinder is firstly simulated,and subsequently numerical simulations of the heat flux and flow field characteristics around the blunt body at different heights are carried out in two different cases:the thermal nonequilibrium condition and the thermochemical nonequilibrium condition.Numerical results demonstrate the validity and reliability of the proposed methods.
基金supported by the National Natural Science Foundation of China(Grant No.50876040)
文摘Using the process parameter description,we analyzed the difference between the characteristics of laminar convections through parallel plain planes with uniform temperature and heat flux.The results show the following.(1)On the wall surface of the developing region,under uniform heat flux boundary condition,the heat flux normal to the wall surface is transported through a convection process although the velocity is zero;the velocity gradient contributes to this transport,but under uniform temperature boundary condition,the heat flux normal to the wall surface is transported through a difussion process.(2)Inside the flow of the developing region,whether under uniform temperature or heat flux boundary condition,the heat flux along the main flow direction and the heat flux normal to the wall surface are transported through a convection process,and the contributions of velocity and velocity gradient are dependent on the thermal boundary condition.(3)On the wall surface of the fully developed region,under uniform heat flux boundary condition,the heat flux normal to the wall surface is transported through a convection process;the velocity gradient contributes to this transport,but under uniform temperature boundary condition,the heat flux normal to the wall surface is transported through a diffusion process.(4)Inside the flow of the fully developed region,under uniform temperature boundary condition,the heat flux along the main flow direction and the heat flux normal to the wall surface are transported through a convection process,and the velocity and velocity gradient contribute to these transports;under uniform heat flux boundary condition,the heat flux along the main flow direction and the heat flux normal to the wall surface are transported through a convection process.Furthermore,the transport of the heat flux along the main flow direction is a no-net convection process;the velocity gradient contributes to the transport of the heat flux only in the normal direction of the wall surface.(5)Simply because the maximum velocity gradient component on the wall surface contributes to the transport of the heat flux normal to the wall surface under uniform heat flux boundary condition,it does not contribute to this transport under uniform temperature boundary condition;thus,the heat transfer intensity under uniform heat flux boundary condition is stronger than that under uniform temperature boundary condition.
