Mach 3.5 Compression Corner Control using Micro-Vortex Generators

An experimental investigation has been performed to examine the effect of vortex generators (VGs) on a compression corner flow separation. Experiments are conducted in a turbulent flow along a 23° compression corner at Mach 3.5 with unit Reynolds number of 44 × 10^6 /m. The effects of micro-ramp, standard ramped-vane, and inverted ramped-vane VGs on the separation are studied. In addition, the effect of device location is examined, with each VG placed 4, 8, and 15 boundary-layer thicknesses (δ) upstream of the compression corner hinge line. The baseline uncontrolled flow has a separation that is approximately 2.2δ in streamwise extent and is relatively two-dimensional near the tunnel centerline. All VGs cause the separation to ripple and become more three-dimensional, but none remove it altogether. Pressure sensitive paint measurements show that significant separation shock corrugation accompanied by small spanwise differences in the separation pressure rise occurs downstream of the VGs. Furthermore, laser Doppler velocimetry measurements show that the VG-induced vortices remain coherent and capable of generating a momentum exchange after passing through the compression corner interaction. The enhanced flow three-dimensionality causes the areas of increased and decreased near-wall momentum to become more intense downstream of reattachment, resulting in significant flow distortion. Surface oil-flow results indicate that vane-type VGs produce a stronger control effect than micro-ramps. Additionally, for a given device location standard vane configurations are more effective at reducing separation size than inverted vanes. Inverted vanes tend to generate large areas of increased low-momentum near the wall that can locally increase the separation length. Standard vane configurations are more effective when placed near the interaction (around 4δ), while inverted vanes produce a more favorable effect when placed farther from the interaction (at distances around 8δ).