TRANSITIONAL SHOCK-WAVE BOUNDARY LAYER INTERACTION OVER A COMPRESSION RAMP

Experiments are performed to study the interaction between shock-waves and a laminar boundary layer on a compression ramp at Mach 1.66. Pitot probe measurements and hot-wire anemometry are complemented with Schlieren visualisation, while Reynolds number is varied by a factor of two. The results suggest a "fully laminar" type of interaction where transition of the boundary layer occurs downstream of reattachment. On the contrary, oblique shock-wave laminar boundary layer interactions resulted in a "transitional" type of interaction with transition occurring at reattachment, for similar freestream conditions and equivalent shock strength. This difference in the type of interaction resulted in subtle deviations in the relative length and time scales of the shockwave boundary layer interaction. The non-dimensional lengths of interactions, based on mass balance across the interaction, were similar for the two geometrical configurations, but the evolution of these length scales with increasing Reynolds number were found to be different. The Strouhal number associated with low frequency unsteadiness matched across both the configurations, with typical time scales associated with transitional mechanisms in oblique shock reflection, "delayed" in the compression ramp measurements