Over the past half century,a variety of computational fluid dynamics(CFD)methods and the direct simulation Monte Carlo(DSMC)method have been widely and successfully applied to the simulation of gas flows for the conti...Over the past half century,a variety of computational fluid dynamics(CFD)methods and the direct simulation Monte Carlo(DSMC)method have been widely and successfully applied to the simulation of gas flows for the continuum and rarefied regime,respectively.However,they both encounter difficulties when dealing with multiscale gas flows in modern engineering problems,where the whole system is on the macroscopic scale but the nonequilibrium effects play an important role.In this paper,we review two particle-based strategies developed for the simulation of multiscale nonequilibrium gas flows,i.e.,DSMC-CFD hybrid methods and multiscale particle methods.The principles,advantages,disadvantages,and applications for each method are described.The latest progress in the modelling of multiscale gas flows including the unified multiscale particle method proposed by the authors is presented.展开更多
This paper systematically reviews the mathematical modeling based on the computational fluid dynamics(CFD)method of equilibrium and nonequilibrium hypersonic flows.First,some physicochemical phenomena in hypersonic fl...This paper systematically reviews the mathematical modeling based on the computational fluid dynamics(CFD)method of equilibrium and nonequilibrium hypersonic flows.First,some physicochemical phenomena in hypersonic flows(e.g.,vibrational energy excitation and chemical reactions)and the flow characteristics at various altitudes(e.g.,thermochemical equilibrium,chemical nonequilibrium,and thermochemical nonequilibrium)are reviewed.Second,the judgment rules of whether the CFD method can be applied to hypersonic flows are summarized for accurate numerical calculations.This study focuses on the related numerical models and calculation processes of the CFD method in a thermochemical equilibrium flow and two nonequilibrium flows.For the thermochemical equilibrium flow,the governing equations,chemical composition calculation methods,and related research on the thermodynamic and transport properties of air are reviewed.For the nonequilibrium flows,the governing equations that include one-,two-,and three-temperature models are reviewed.The one-temperature model is applied to a chemical nonequilibrium flow,whereas the two-and three-temperature models are applied to a thermochemical nonequilibrium flow.The associated calculations and numerical models of the thermodynamic and transport properties,chemical reaction sources,and energy transfers between different energy modes of the three models are presented in detail.Finally,the corresponding numerical models of two special wall boundary conditions commonly used in hypersonic flows(i.e.,slip boundary conditions and catalytic walls)and related research,are reviewed.展开更多
The accurate prediction of the aeroheating performance of hypersonic vehicles requires more detailed modeling of the catalysis process,rather than merely employing a catalytic coefficient.In this paper,the theoretical...The accurate prediction of the aeroheating performance of hypersonic vehicles requires more detailed modeling of the catalysis process,rather than merely employing a catalytic coefficient.In this paper,the theoretical modeling,as well as the direct simulation Monte Carlo method,is used to preliminarily study the incomplete chemical energy accommodation effects,that is,only a part of the potential energy released in the heterogenous recombination reaction is transferred to the surface,while the remaining is retained as the vibrational energy of the desorbed molecule.An integrated model is proposed to describe the contribution of each energy mode in the rarefied nonequilibrium heat and mass transfer process.Based on the model and several Damko?hler numbers,an analytical formula is derived,and is also shown to compare well with the numerical results.On account of the incomplete accommodations of the chemical and vibrational energy on the wall,a variation up to 20%is observed in predicting the stagnation point heat flux under typical nonequilibrium flow conditions.This study could enrich our understanding of the nonequilibrium heat transfer phenomenon and also shows a potential practical value.展开更多
基金National Numerical Windtunnel Project(Grant 2018-ZT3A05)National Natural Science Foundation of China(Grant No.11772034)Engineering and Physical Sciences Research Council(EPSRC,Grant No.EP/N016602/1).
文摘Over the past half century,a variety of computational fluid dynamics(CFD)methods and the direct simulation Monte Carlo(DSMC)method have been widely and successfully applied to the simulation of gas flows for the continuum and rarefied regime,respectively.However,they both encounter difficulties when dealing with multiscale gas flows in modern engineering problems,where the whole system is on the macroscopic scale but the nonequilibrium effects play an important role.In this paper,we review two particle-based strategies developed for the simulation of multiscale nonequilibrium gas flows,i.e.,DSMC-CFD hybrid methods and multiscale particle methods.The principles,advantages,disadvantages,and applications for each method are described.The latest progress in the modelling of multiscale gas flows including the unified multiscale particle method proposed by the authors is presented.
基金Key Laboratory of Hypersonic Aerodynamic Force and Heat Technology of the AVIC Aerodynamics Research Institute,National Natural Science Foundation of China(Grant Nos.31371873,31000665,51176027,and 31300408)Special Program for Applied Research on Super Computation of the NSFC-Guangdong Joint Fund(the second phase)of China and CAST-BISEE(Beijing Institute of Spacecraft Environment Engineering)innovation fund.
文摘This paper systematically reviews the mathematical modeling based on the computational fluid dynamics(CFD)method of equilibrium and nonequilibrium hypersonic flows.First,some physicochemical phenomena in hypersonic flows(e.g.,vibrational energy excitation and chemical reactions)and the flow characteristics at various altitudes(e.g.,thermochemical equilibrium,chemical nonequilibrium,and thermochemical nonequilibrium)are reviewed.Second,the judgment rules of whether the CFD method can be applied to hypersonic flows are summarized for accurate numerical calculations.This study focuses on the related numerical models and calculation processes of the CFD method in a thermochemical equilibrium flow and two nonequilibrium flows.For the thermochemical equilibrium flow,the governing equations,chemical composition calculation methods,and related research on the thermodynamic and transport properties of air are reviewed.For the nonequilibrium flows,the governing equations that include one-,two-,and three-temperature models are reviewed.The one-temperature model is applied to a chemical nonequilibrium flow,whereas the two-and three-temperature models are applied to a thermochemical nonequilibrium flow.The associated calculations and numerical models of the thermodynamic and transport properties,chemical reaction sources,and energy transfers between different energy modes of the three models are presented in detail.Finally,the corresponding numerical models of two special wall boundary conditions commonly used in hypersonic flows(i.e.,slip boundary conditions and catalytic walls)and related research,are reviewed.
基金supported by the National Key Research and Development Program of China (Grant No.2019YFB1704204)the National Natural Science Foundation of China (Grant No.12002348).
基金supported by the National Natural Science Foundation of China (Nos. 11672292 and 12072343)the Youth Innovation Promotion Association of Chinese Academy of Sciences (No. 2017490)the Strategic Priority Research Program (B) of Chinese Academy of Sciences (No. XDB22040202)
文摘The accurate prediction of the aeroheating performance of hypersonic vehicles requires more detailed modeling of the catalysis process,rather than merely employing a catalytic coefficient.In this paper,the theoretical modeling,as well as the direct simulation Monte Carlo method,is used to preliminarily study the incomplete chemical energy accommodation effects,that is,only a part of the potential energy released in the heterogenous recombination reaction is transferred to the surface,while the remaining is retained as the vibrational energy of the desorbed molecule.An integrated model is proposed to describe the contribution of each energy mode in the rarefied nonequilibrium heat and mass transfer process.Based on the model and several Damko?hler numbers,an analytical formula is derived,and is also shown to compare well with the numerical results.On account of the incomplete accommodations of the chemical and vibrational energy on the wall,a variation up to 20%is observed in predicting the stagnation point heat flux under typical nonequilibrium flow conditions.This study could enrich our understanding of the nonequilibrium heat transfer phenomenon and also shows a potential practical value.
