Numerical Simulation of Weakly Ionized Dynamic Plasma for Reentry Vehicles

Abstract

Past studies of plasma sheaths enveloping vehicles have shown that the distribution of plasma is time-varying and results in communication and navigation problems. This paper aims to investigate the dynamic characteristics of the plasma sheath through the simulations of the Radio Attenuation Measurements-C II vehicle and the Apollo command module flowfields. The numerical methodology is based on the unsteady Reynolds-averaged Navier–Stokes model and the detached-eddy simulation model, and the thermochemical nonequilibrium effect is considered. The stable flows of both vehicles with a steady plasma sheath widely distributed in the shock-wave layer are first obtained. For the Radio Attenuation Measurements-C II vehicle, the dynamic plasma arising from the vehicle pitching oscillation has the same frequency as the vehicle oscillation, and the magnitude of the disturbance to plasma is related to the oscillation velocity. For the Apollo command module, the oscillation period of the electron density is the same as the evolution period of the vortex structures in the leeward regions. The time-varying surface electron density and pressure reveal a similar variation trend with the phase difference. In addition, the periodicity of the dynamic plasma disappears as the flow instability intensifies in the Apollo command module flowfields, whereas periodic plasma exists for a long time in the Radio Attenuation Measurements-C II vehicle oscillation flowfields.