Parabolized Stability Analysis of Hypersonic Thermal-Chemical Nonequilibrium Boundary-Layer Flows

In this work, the stability of Mach 20 flows past a 6 deg wedge in thermal-chemical nonequilibrium (TCNE) is studied by means of linear parabolized stability equations (PSEs) in combination with advanced thermodynamic and transport models. First, verifications are performed against existing numerical results in the literature. Good agreement is achieved in two benchmark cases. The present PSE results match the direct numerical simulation data from the literature fairly well, especially for the growth-rate oscillation behavior of the supersonic mode disturbance. Then, we investigate the TCNE effects on the supersonic mode instabilities over the 6 deg wedge. It is found that the flow stability is affected mainly by the TCNE effect on mean flows rather than that on disturbances. Subsequently, more PSE calculations are carried out with a variation of wall temperatures and disturbance frequencies. With the wall temperature beyond 30% of the adiabatic one, the unstable supersonic mode is found to return to the subsonic one. Downstream of this turning point, the disturbance growth-rate oscillation dramatically decays. With the increase of the disturbance frequency, a similar trend to wall heating is observed in the growth-rate and phase velocity curves.