Intrinsic three-dimensionality of laminar hypersonic shock wave/boundary layer interactions

A high-fidelity numerical investigation has been conducted into the nature of 3D instabilities intrinsic to a hypersonic, laminar, shock wave/ boundary layer interaction (SWBLI) flow over an axi-symmetric body at zero incidence to the oncoming stream. The results identify a distinct bifurcation point from steady state, quasi-2D conditions to a 3D unsteady system. Detailed numerical experiments have revealed that the formation of a secondary vortex beneath the primary vortex within the separation bubble is responsible for triggering longitudinal, Görtler-like, vortex structures within this subsonic region. It has been found that these separation bubble vortices force the shear layer bounding this region, with the effects of this forcing producing the experimentally observed striations in heat flux when the shear layer reattaches to the model surface. These results cast new light on the source of instability within SWBLI flows and may prove fundamental in the development of a full understanding of transitional SWBLI flows.