DSMC hypersonic reentry flow simulations with photon Monte Carlo radiation

Earth re-entering spacecrafts at high Mach numbers generate a strong shock region ahead of the blunt body with a temperature above 60,000 K. These extreme Mach number flows are suffciently energetic to initiate gas ionization and thermal and chemical ablation processes. The electronically excited and ionized particles affect the nonequilibrium atomic and molecular energy distributions and radiation within the shock layer. In this work, we present the first direct simulation Monte Carlo (DSMC) simulations coupled with the finite volume photon Monte Carlo (FV-PMC) method to simulate Stardust reentry flows from continuum to the transitional flow regime. Eleven species including five ionization processes were modeled in DSMC, and the average ion velocity model was used to simulate a quasi-neutral flow. To efficiently capture the high nonequilibrium effects, emission and absorption coefficient database based on the Nonequilibrium Air Radiation (NEQAIR) model were generated, and radiation from atomic N and O species was calculated by the FV-PMC method. As a check on the numerical accuracy of the FV-PMC method and its implementation the results were compared with those of the conventional radiative heat transport equation solver using the NEQAIR database for the Stardust flowfield generated in our previous work. The radiative heat source calculated by the FV-PMC method is loosely coupled with DSMC flow simulations. For all flow regimes, the radiation influences the flowfield. The high emission energy leads to a decrease in gas temperature in the shock layer and a decrease in the convective heat flux to the Stardust body.