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An Efficient Nonlinear Multigrid Solver for the Simulation of rarefied gas Cavity flow

Communications in Computational Physics 2023年第7期34卷 357-391页

作者： Zhicheng Hu Guanghan Li School of Mathematics Nanjing University of Aeronautics and AstronauticsNanjing 211106China Key Laboratory of Mathematical Modelling and High Performance Computing of Air Vehicles(NUAA) MIITNanjing 211106China

We study efficient simulation of steady state for multi-dimensional rarefied gas flow,which is modeled by the Boltzmann equation with BGK-type collision term.A nonlinear multigrid solver is proposed to resolve the efficiency issue by the following *** unified framework of numerical regularized moment method is first adopted to derive the high-quality discretization of the underlying problem.A fast sweeping iteration is introduced to solve the derived discrete problem more efficiently than the usual time-integration scheme on a single level *** it as the smoother,the nonlinear multigrid solver is then established to significantly improve the convergence *** OpenMP-based parallelization is applied in the implementation to further accelerate the *** experiments for two lid-driven cavity flows and a bottom-heated cavity flow are carried out to investigate the performance of the resulting nonlinear multigrid *** results show the wonderful efficiency and robustness of the solver for both first-and second-order spatial discretization.

关键词： Boltzmann equation moment method multigrid rarefied gas flow steady state

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DIRECT NUMERICAL TEST OF THE B-G-K MODEL EQUATION BY THE DSMC METHOD

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Acta Mechanica Sinica 2000年第2期16卷 133-140页

作者：沈青易志强 Institute of Mechanics Chinese Academy of Sciences Beijing China 100080

In the present paper the rarefied gas how caused by the sudden change of the wall temperature and the Rayleigh problem are simulated by the DSMC method which has been validated by experiments both in global flour field and velocity distribution function level. The comparison of the simulated results with the accurate numerical solutions of the B-G-K model equation shows that near equilibrium the BG-K equation with corrected collision frequency can give accurate result but as farther away from equilibrium the B-G-K equation is not accurate. This is for the first time that the error caused by the B-G-K model equation has been revealed.

关键词： BGK model equation DSMC method rarefied gas flow Rayleigh problem

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Effects of Carbon Fiber gas Pressure,Temperature and Deposition Distance on Thermo Fluids Phenomena in Vacuum Deposition Machine

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Journal of Thermal Science 2008年第3期17卷 253-260页

作者： Ying HE M.Ota S.K.Stefanov Dept. Mech. Eng. Tokyo Metropolitan University 1-1 Minami-Osawa Hachioji-shi Tokyo 192-0397 Japan Institute of Mechanics BASci. Acad. G Bonchev Str. B1.4 Sofia 1113 Bulgaria

A numerical analysis method （DSMC, Direct Simulation Monte Carlo）[1] was developed to simulate the molecular motion of rarefied gases. In the present paper, numerical approaches by the DSMC method have been carded out. By the computation model of CC-40F carbon coater, the cylindrical deposition machine has axial symmetry; the flows inside the vacuum chamber were analyzed. The substrates were put on the bottom and the fiber near the ceiling in the computational domain. In the computational model, air and carbon molecules are working ones. The effects of the air gas pressure variation in the chamber, the effects of the deposition distance variation and the surface temperature variation of the carbon fiber on thermo fluids phenomena are discussed and visualized. Changing the number density of carbon and air, the temperature of the carbon and the velocity of the carbon in the chamber are discussed. With changing the surface temperature of the carbon fiber, qualitative assay of experiment and simulation result is in similar trend very well. The DSMC method is a forceful tool for the study of rarefied gas flow in vacuum deposition machine.

关键词： rarefied gas flow Knudsen number DSMC method vacuum carbon deposition MEMS

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Rotational Slip flow in Coaxial Cylinders by the Finite-Difference Lattice Boltzmann Methods

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Communications in Computational Physics 2011年第5期9卷 1293-1314页

作者： Minoru Watari LBM Fluid Dynamics Laboratory 3-2-1 Mitahora-higashiGifu 502-0003Japan

Recent studies on applications of the lattice Boltzmann method(LBM)and the finite-difference lattice Boltzmann method(FDLBM)to velocity slip simulations are mostly on one-dimensional(1D)problems such as a shear flow between parallel *** to a 2D problem may raise new *** author performed numerical simulations of rotational slip flow in coaxial cylinders as an example of 2D *** types of 2D models were *** first were multi-speed FDLBM models proposed by the *** second was a standard LBM,the D2Q9 *** simulations were performed applying a finite difference scheme to both the *** study had two *** first was to investigate the accuracies of LBM and FDLBM on applications to rotational slip *** second was to obtain an experience on application of the cylindrical coordinate *** FDLBM model with 8 directions and the D2Q9 model showed an anisotropic flow pattern when the relaxation time constant or the Knudsen number was *** FDLBM model with 24 directions showed accurate results even at large Knudsen numbers.

关键词： Finite-difference lattice Boltzmann method rarefied gas flow rotational slip flow cylindrical coordinate

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