MAE Department - PG seminar  - Stability of Hypersonic Shock-Induced Separated Flow

The stability of hypersonic shock-wave/boundary-layer interactions over a compression corner is investigated using global stability analysis and direct numerical simulations. The global stability boundary is determined over a wide range of flow governing parameters and correlated with a scaled deflection angle based on triple-deck theory. Beyond a critical angle, the nominally two-dimensional base flow becomes globally unstable to three-dimensional perturbations. Amplification of the leading mode generates pairs of counterrotating streamwise vortices inside the separation region and downstream of reattachment. As the flow is further destabilized, the global instability can trigger laminar‒turbulent transition in the reattached boundary layer. The response of globally stable flow to upstream harmonic disturbances is then examined using global resolvent analysis. The optimal disturbances are in the form of steady streamwise streaks, which originate from transient growth in the incoming boundary layer due to the lift-up mechanism and grow across the interaction region due to the Görtler instability. Potential routes to turbulence in hypersonic shock-induced separated flow are presented.