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The direct simulation Monte Carlo (DSMC) method is performed to simulate the thermochemical non-equilibrium flow from 130 km to 70 km across outer space free molecular, rarefied transitional and near-continuum regime during the reentry module entering the atmosphere. The developed hybrid spatial Cartesian and unstructured triangular surface meshes and adaptive refinements are used in the computation. The variable time step simulation strategy for the coexistence of high rarefied flow to near-continuum flow and domain decomposition parallel DSMC algorithm are established to investigate the evolution of shock wave layer and boundary layer across different flow regimes. The effects of rarefied gas and high temperature real gas on module aerodynamic and trim characteristics are simulated and analyzed. The impacts of different surface reflection model and mass center location offsets on the trim property are also computed and analyzed. The calculated trim angles of attack have good agreement with the flight data for lunar explanation test reentry module. The computation results show that the rarefied gas effects and surface reflection model have significantly impact on aerodynamic and trim characteristics above altitude of 90 km. The real gas effects have great impact on aerodynamics helow altitude of 90 km. The lateral offset of centroid has a larger impact on the trim angle of attack. [ABSTRACT FROM AUTHOR]

In order to simulate gas flows with complex shapes or several bodies covering various regimes, coordinate space should be divided into dinky cells, and numerical method based on the complex mesh system should also be developed. In this paper, two-dimensional flows around complex objects are described by multi-block patched meshes, and then body-fitted mesh systems are given. Boltzmann-Rykov model equation involving rotational non-equilibrium effect is numerically computed based on this mesh system. Discrete velocity ordinate method is used to disperse velocity space, while finite-difference NND scheme for coordinate space. Transfer of distribution function on the interface, information and velocity information on the grid included, should be treated especially. Then flow characters from rarefied transition to continuum around complex bodies are obtained by numerical computing. Some examples show that macro-parameters glossily translate between different blocks in the whole mesh system. Results from GKUA are compared with those from reference and DSMC method. It is showed that the Gas-kinetic Unified Algorithm based on multi-block patched mesh is credible to numerically simulate complex flows in various regimes. [ABSTRACT FROM AUTHOR]