Multiscale particle-continuum simulations of hypersonic flow over a planetary probe

A modular particle-continuum numerical method is used to simulate the flow over a 70 deg blunted cone planetary probe geometry under various steady-state hypersonic conditions. The conditions studied correspond to low global Knudsen number flow where hypersonic velocities induce a large range of temporal and spatial scales that must be modeled. The modular particle-continuum algorithm loosely couples direct simulation Monte Carlo and Navier-Stokes methods, which operate in nonequilibrium and continuum regions, respectively. In addition, particle and continuum regions have different mesh densities and are updated using different sized time steps. Modular particlecontinuum simulations are shown to reproduce the heating rates, velocity slip, and thermal nonequilibrium on the probe surface, as well as the flowfield properties predicted by the direct simulation Monte Carlo method with high accuracy. For the first time, such a hybrid particle-continuum method is shown to achieve high accuracy while achieving an order of magnitude decrease in required computational time and memory compared with pure particle simulation. The modular particle-continuum simulations agree well with Navier-Stokes simulations and experimental measurements in the dense forebody flow. In the rarefied wake of the planetary probe, the modular particle-continuum results are in better agreement with experimental measurements than Navier-Stokes simulations.