Influence of a Microramp Array on a Hypersonic Shock-Wave/Turbulent Boundary-Layer Interaction

Experiments were performed to study the effects of an array of microramp sub-boundary-layer vortex generators on a hypersonic shock/turbulent boundary-layer interaction. Two staggered rows of microramps were installed upstream of a 33 deg compression-corner interaction with large-scale separation at Mach 7.2, and the influence of these devices on the mean and turbulent flowfield, and the separation region in particular, was studied with particle image velocimetry. The microramps strongly altered the mean flow topology: The previously two-dimensional interaction region with a large separated zone in the vicinity of the ramp corner is broken up into a three-dimensional interaction, where the mean velocity at the spanwise locations downstream of the microramp centerlines is decreased, whereas it is increased at the spanwise locations in between the microramp vertices. The mean overall separation length is reduced, most strongly at spanwise locations in between microramps. A narrow local increase occurs directly downstream of the device vertices. The turbulence behavior across the interaction is not fundamentally altered under the influence of vortex-generator control, but a superposition of effects is observed. The microramp-induced longitudinal vortex pairs increase turbulent mixing and, by adding momentum into the near-wall region, support a faster decrease of turbulence intensity and return to equilibrium conditions downstream of the interaction.