The effects of energy accommodation of reflected gas molecules on flow structures during expired spacecraft reentry

Abstract

To study the influence of energy accommodation of scattering gas molecules on flow fields during large expired spacecraft reentry, a more elaborated gas-surface interaction model, compared with full Maxwellian diffuse model, is employed in implicit algorithms based on Boltzmann model equation. The characteristic distributions around cylinder at different fluid regimes are accordingly obtained by implicit algorithms, Navier-Stokes solver and DSMC ((Direct Simulation Monte Carlo) method. And the consistency of these results is verified. It is confirmed that present algorithms are capable of solving external flow problems covering various fluid regimes. Then the simulation results see that under current conditions set in the paper, pressure and temperature are proportional to wall activation ($\omega =T_w/T_{\infty }$, $T_w$ is surface temperature, $T_{\infty }$ denotes as free stream temperature), but their amplitudes alter with $\omega$ at different fluid regimes. As for the effects of energy accommodation coefficients (${\alpha }_e$), both pressure and temperature profiles vary in a linear way with ${\alpha }_e$. However, the variation ranges of these parameters are diverse with regard to different fluid regimes. These observations are favor to the construction of efficient forecasting software, which could predict the flight path of large defunct spacecraft. In this forecasting software, the external ballistics computations and aerothermodynamic simulations are synchronously carried out.