Coupled DSMC-PMC radiation simulations of a hypersonic reentry

During extreme-Mach-number reentry into Earth's atmosphere, spacecraft experience hypersonic nonequilibrium flow conditions that dissociate molecules and ionize atoms. Since the electronic levels of atomic species are strongly excited for high-Mach-number conditions, the radiative contribution to the total heat load can be significant. To perform accurate and efficient analyses of chemically reacting flowfield-radiation interactions, the direct simulation Monte Carlo (DSMC) and the photon Monte Carlo (PMC) radiative transport methods are used to simulate flowfield-radiation coupling from transitional to peak heating freestream conditions. The first DSMC-finite-volume PMC simulations are presented with the goal of understanding the effect of radiation on the flow structure for different degrees of hypersonic nonequilibrium. It is found that, except for the highest altitudes, the coupling of radiation influences the flowfield leading to a decrease in both heavy particle translational and internal temperatures and a decrease in the convective heat flux to the body. The DSMC-PMC coupled simulations are compared with the previous coupled simulations and correlations obtained using continuum flow modeling and onedimensional radiative transport. The DSMC simulations are also extended to consider the effect of gas-surface interactions on the convective heat flux.