Streamline curvature driven transition to turbulence in axisymmetric hypersonic shock wave boundary layer interactions

We investigate the origin of unsteady fluctuations in separation bubbles preceding turbulent transition in hypersonic flows over axisymmetric cone flare geometries. We utilize direct numerical simulations and input-output analysis to identify the physical mechanism driving the amplification of these perturbations. Our analysis reveals that azimuthally asymmetric waves dominate the unsteady response within the axisymmetric separated shear layer, with their growth arising from a centrifugal amplification mechanism created by the streamline curvature inherent to cone flare geometry. These centrifugal waves play a critical role in the transition process, with amplification strongly dependent on the cone flare angle through its effect on streamline curvature. We investigate how Reynolds number and freestream noise characteristics influence these growth rates, providing fundamental insight into the transition physics of separated hypersonic flows and explaining the origin of azimuthally asymmetric perturbations in cone flare SWBLI.