A multiscale stochastic-deterministic coupling method is proposed to investigate the complex interactions between turbulent and rarefied gas flows within a unified framework.This method intermittently integrates the g...A multiscale stochastic-deterministic coupling method is proposed to investigate the complex interactions between turbulent and rarefied gas flows within a unified framework.This method intermittently integrates the general synthetic iterative scheme with the shear stress transport turbulence model into the direct simulation Monte Carlo(DSMC)approach,enabling the simulation of gas flows across the free-molecular,transition,slip,and turbulent regimes.First,the macroscopic synthetic equations,derived directly from DSMC,are coupled with the turbulence model to establish a constitutive relation that incorporates not only turbulent and laminar transport coefficients but also higher-order terms accounting for rarefaction effects.Second,the macroscopic properties,statistically sampled over specific time intervals in DSMC,along with the turbulent properties provided by the turbulence model,serve as initial conditions for solving the macroscopic synthetic equations.Finally,the simulation particles in DSMC are updated based on the macroscopic properties obtained from the synthetic equations.Numerical simulations demonstrate that the proposed method asymptotically converges to the turbulence model in the continuum regime and to the DSMC method in the rarefied regime,depending on the Knudsen number.This coupling method is then applied to simulate a turbulent opposing jet surrounded by hypersonic rarefied gas flows,revealing significant variations in surface properties due to the interplay of turbulent and rarefied effects.展开更多
As a Group III–V compound, GaInP is a high-efficiency luminous material. Metal organic chemical vapor deposition (MOCVD) technology is a very efficient way to uniformly grow multi-chip, multilayer and large-area thin...As a Group III–V compound, GaInP is a high-efficiency luminous material. Metal organic chemical vapor deposition (MOCVD) technology is a very efficient way to uniformly grow multi-chip, multilayer and large-area thin film. By combining the computational fluid dynamics (CFD) and the kinetic Monte Carlo (KMC) methods with virtual reality (VR) technology, this paper presents a multiscale simulation of fluid dynamics, thermodynamics, and molecular dynamics to study the growth process of GaInP thin film in a vertical MOCVD reactor. The results of visualization truly and intuitively not only display the distributional properties of the gas’ thermal and flow fields in a MOCVD reactor but also display the process of GaInP thin film growth in a MOCVD reactor. The simulation thus provides us with a fundamental guideline for optimizing GaInP MOCVD growth.展开更多
Numerical simulation of complex flow fields with multi-scale structures is one of the most important and challenging branches of computational fluid dynamics. From linear analysis and numerical experiments it has been...Numerical simulation of complex flow fields with multi-scale structures is one of the most important and challenging branches of computational fluid dynamics. From linear analysis and numerical experiments it has been discovered that the higher-order accurate method can give reliable and efficient computational results, as well as better resolution of the complex flow fields with multi-scale structures. Compact finite difference schemes, which feature higher-order accuracy and spectral-like resolution with smaller stencils and easier application of boundary conditions, has attracted more and more interest and attention.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.12450002)。
文摘A multiscale stochastic-deterministic coupling method is proposed to investigate the complex interactions between turbulent and rarefied gas flows within a unified framework.This method intermittently integrates the general synthetic iterative scheme with the shear stress transport turbulence model into the direct simulation Monte Carlo(DSMC)approach,enabling the simulation of gas flows across the free-molecular,transition,slip,and turbulent regimes.First,the macroscopic synthetic equations,derived directly from DSMC,are coupled with the turbulence model to establish a constitutive relation that incorporates not only turbulent and laminar transport coefficients but also higher-order terms accounting for rarefaction effects.Second,the macroscopic properties,statistically sampled over specific time intervals in DSMC,along with the turbulent properties provided by the turbulence model,serve as initial conditions for solving the macroscopic synthetic equations.Finally,the simulation particles in DSMC are updated based on the macroscopic properties obtained from the synthetic equations.Numerical simulations demonstrate that the proposed method asymptotically converges to the turbulence model in the continuum regime and to the DSMC method in the rarefied regime,depending on the Knudsen number.This coupling method is then applied to simulate a turbulent opposing jet surrounded by hypersonic rarefied gas flows,revealing significant variations in surface properties due to the interplay of turbulent and rarefied effects.
基金supported by the National Natural Science Foundation of China (Grant No. 60706014)the National Science Fund for Distinguished Young Scholars (Grant No. 60625302)+2 种基金the National Natural Science Foundation of China (General Program) (Grant No. 2009CB320603)the National High-Tech Research and Development Program of China (Grant No. 2009AA04Z159)the Shanghai Leading Academic Discipline Project (Grant No. B504)
文摘As a Group III–V compound, GaInP is a high-efficiency luminous material. Metal organic chemical vapor deposition (MOCVD) technology is a very efficient way to uniformly grow multi-chip, multilayer and large-area thin film. By combining the computational fluid dynamics (CFD) and the kinetic Monte Carlo (KMC) methods with virtual reality (VR) technology, this paper presents a multiscale simulation of fluid dynamics, thermodynamics, and molecular dynamics to study the growth process of GaInP thin film in a vertical MOCVD reactor. The results of visualization truly and intuitively not only display the distributional properties of the gas’ thermal and flow fields in a MOCVD reactor but also display the process of GaInP thin film growth in a MOCVD reactor. The simulation thus provides us with a fundamental guideline for optimizing GaInP MOCVD growth.
文摘Numerical simulation of complex flow fields with multi-scale structures is one of the most important and challenging branches of computational fluid dynamics. From linear analysis and numerical experiments it has been discovered that the higher-order accurate method can give reliable and efficient computational results, as well as better resolution of the complex flow fields with multi-scale structures. Compact finite difference schemes, which feature higher-order accuracy and spectral-like resolution with smaller stencils and easier application of boundary conditions, has attracted more and more interest and attention.
