Direct numerical simulation of gas-surface interactions within a turbulent reacting hypersonic boundary layer*

Viscous dissipation in high-Mach hypersonic boundary layers activates non-equilibrium thermochemical processes in the form of internal-energy excitation and dissociation/recombination phenomena. With the characteristic rates of gas-phase chemical reactions comparable to those of integral-scale turbulent fluctuations, the chemical production rates of radical species are significantly modulated by turbulent mixing of thermodynamic states in hypersonic boundary layers. In this work, we present direct numerical simulation results for a high-temperature turbulent boundary layer overriding an ablative boundary with oxidation, nitridation, and sublimation surface reactions. Statistical analysis of turbulence/chemistry interaction is presented for both surface chemistry and gas-phase processes involving ablation products. Analysis of reaction-rate closure modeling for coarse-grained computations is conducted a priori, with a particular emphasis on representations for subfilter reactive processes in the context of large-eddy simulation.