Comparative Analysis of Thermophysics Models for the Simulations of Nonequilibrium Flow

Advances in computational capabilities have allowed for the calculation of canonical hypersonic flows using the direct molecular simulation method. DMS is a particle method that uses quantum mechanically derived interaction potentials to simulate molecular collisions within a flow field. Since these interaction potentials are the only modeling inputs used in the simulation, all flow features can solely be attributed to the ab initio potential energy surfaces. The fundamental nature of these simulations lends to be used as benchmarks to assess lower fidelity models. In this work we investigated two canonical hypersonic flows, where the dominant gas-phase chemical activity was the dissociation of free stream diatomic species: (a) Mach 21 nitrogen flow over a blunt wedge and (b) Mach 8.2 oxygen flow over a double cone geometry. For the comparative analysis we consider seven actively used CFD codes and five thermochemical models. It is observed that new generation of thermochemistry models based in ab initio provide solutions that are more physical and compare favorably to the first principles DMS.