Abstract:
In view of the multi-scale non-equilibrium flows around the re-entry spacecraft (module) during re-entering process, the physical analysis and computable modelling of the collision integral based on the Boltzmann equation are summarized. The unified Boltzmann model equation is constructed with the consideration of the complete gas, the rotational non-equilibrium, and the thermodynamic non-equilibrium effects involving in vibrational energy excitation. And then, the gas-kinetic unified algorithm (GKUA) and the parallel computing platform for the re-entry aerothermodynamics and flows of spacecraft re-entry module are established. As verification and combination of different methods, the DSMC method for re-entry non-equilibrium flow of thermo-chemical ionized gas, the N-S/DSMC hybrid algorithm in the near-continuum transitional flow regimes, the N-S equation solver modified by the slip boundary flow theory, the low-density wind tunnel experiments and so on are briefly described, and the integrated simulation platform has been established for aerodynamics covering various flow regimes from the outer space free-molecule flow to the near-ground continuum flow based on the verification and supplement of the GKUA, DSMC, N-S/DSMC, slip N-S solver and the low-density wind tunnel test. This platform is used to compute the rarefied transition flows around the sphere during the re-entry from
H=110~30 km, the hypersonic tip front edge hollow column skirt, and the comparative analysis of the computation and experiment for the aerothermodynamics and attitude-balance flow problems of the spacecraft capsule. It is proved that the unified algorithm is in good agreement with the DSMC in the high rarefied flow regime, and also consistent with the (slip) N-S solver in the continuum flow regime. And the GKUA is also consistent with the N-S/DSMC algorithm in simulating the flows from the intermediate transition flow regime, and the GKUA has the coincident convergence in solving the flows from the whole flight flow regimes. The adaptability characteristics and prospects of several simulation methods for aerodynamics covering various flow regimes are briefly described, and the varying law of complex hypersonic flows is revealed during the re-entry process of the re-entry module.