Nonlinear PSE Transition Predictions in Hypersonic Boundary Layers with Finite-Rate Chemical Reactions

Abstract

Transition on a Mach 10 adiabatic flat-plate boundary layer is analyzed by means of nonlinear parabolized stability equations (NPSE). To the best of authors’ knowledge, for the first time NPSE are derived and applied to the study of a finite-rate chemically reacting flow. A fundamental breakdown transition mechanism is investigated within two flow assumptions: a frozen and a 5-species chemical nonequilibrium air mixture. The set of hypotheses deployed modifies the predicted perturbation-amplitude evolution, as well as the types of harmonics that are excited. This results in an earlier predicted transition onset in the case of a chemically reacting flow. The effect of chemical reactions is confirmed to be predominant in the base flow, while it is weak on the perturbation field. In particular, the chemically driven modification of the disturbance quantities shows a tendency to slightly increase perturbation amplitudes, contrary to what previous linear N-factor predictions revealed. Moreover, they lead to the appearance of a second distortion region of the boundary-layer temperature field, localized close the wall.