Hybrid Particle-Continuum Simulations of Low Knudsen Number Hypersonic Flows

A modular particle-continuum (MPC) numerical method is used to simulate steady-state hypersonic flows which exhibit local regions of non-equilibrium embedded within mainly continuum flow fields. The MPC method loosely couples direct simulation Monte Carlo (DSMC) and Navier-Stokes (NS) methods which operate in different regions, use different mesh densities, and are updated using different sized timesteps. The MPC method is applied to both a hollow cylinder flare and planetary probe geometry and results are compared with full NS and DSMC simulations as well as with experimental data. MPC simulations are demonstrated to reproduce experimental and full DSMC simulation results for surface and flow field properties including velocity slip, temperature jump, thermal non-equilibrium, heating rates, and pressure distributions with high accuracy. The hollow cylinder flare problem provides an insightful test case for the MPC method, however, it is found un-suitable for practical hybrid simulation. Orders of magnitude variation in mean-free-path for the planetary probe problem make it an excellent candidate for hybrid simulation. For this case, MPC results are obtained approximately 12.5 times faster than a full DSMC simulation while requiring 20% of the memory.