Thermochemical nonequilibrium effects on high-enthalpy double-wedge flows

A hypersonic laminar flow over double wedges with a fixed forward angle of 15 and varied aft angles is studied using computational fluid dynamics and global stability analysis (GSA) at a free-stream Mach number of 12.82 and a total enthalpy of 21.77 MJ/kg. The specific total enthalpy is high enough to trigger evident vibrational excitation and air chemistry. To assess the effects of thermal and chemical nonequilibrium, three different thermochemistry models of air are considered, including frozen, thermal nonequilibrium, and thermochemical nonequilibrium gases. Two-dimensional base-flow simulations indicate that the onset of incipient and secondary separation is insensitive to the inclusion of thermochemistry, although the size of the separation region is substantially reduced. GSA is then performed on the base flows and identifies a three-dimensional stationary global instability beyond a critical aft angle, which is also insensitive to thermochemical nonequilibrium. The criterion of the global stability boundary established for the supersonic flow over compression corners in a calorically perfect gas in terms of a scaled deflection angle [Hao et al., Occurrence of global instability in hypersonic compression corner flow, J. Fluid Mech. 919, A4 (2021)] is, thus, extended to high-enthalpy conditions. Published under an exclusive license by AIP Publishing.

Automated summary

This study investigates hypersonic laminar flow over double wedges using computational fluid dynamics and global stability analysis. The research reveals that thermal and chemical nonequilibrium have minimal effects on the onset of separation in high-enthalpy conditions. Furthermore, the study extends the criterion of global stability to hypersonic flow under high-enthalpy conditions.