Computational Approach for Direct Simulation of High-Enthalpy Turbulent Hypersonic Flows in Thermochemical Nonequilibrium*

Aerodynamic heating in hypersonic turbulent boundary layers at high enthalpies induces finite-rate thermochemical processes, including dissociation and vibrational-electronic relaxation. A novel computational framework is presented to enable fundamental studies of these phenomena via direct numerical simulation of canonical hypersonic turbulent flows at high enthalpies. The framework is based on a two-temperature description of the conservation equations discretized with finite differences. A high-order Euler flux reconstruction procedure is utilized in conjunction with second-order treatment of diffusive terms, while explicit time marching is performed using a strong-stability-preserving Runge Kutta method. Boundary conditions are enforced via the extended Navier-Stokes characteristic boundary conditions to account for dissociation and vibrational-electronic relaxation. This framework is implemented in the Hypersonics Task-based Research solver (Di Renzo et al., Comp. Phys. Comm. 255, 2020) and its performance is evaluated in thermochemical regimes ranging from near-equilibrium to strong nonequilibrium in canonical hypersonic flows.