Mitigation of shock-induced flow separation over an axisymmetric flared body using ramped vanes

This paper brings out the ability of `ramped vane (RV)' vortex generators in attenuating a shock-induced flow separation near an axisymmetric compression corner. Investigations were performed at Mach 2 over a cone-cylinder-flare geometry, with a flow deflection angle of 24 degrees at the cylinder-flare juncture. The boundary layer thickness (delta) at the corner location was estimated to be 5 mm. A circumferential array of RVs was positioned 50 mm (10 delta) upstream of the corner and their trailing edge height (h) was 2.8 mm, which was two-third of the local boundary layer thickness (h = 0.67d(RV)). The RVs produced streamwise counter-rotating vortices that replaced the low-momentum fluid near the model surface with high-momentum fluid from the outermost parts of the boundary layer. As a result, the onset of the interaction/separation was delayed throughout the entire circumference of the model. The interaction's average upstream influence length was reduced by 36%, and the average thickness of the separation region was reduced by about 45%. The surface flow patterns also revealed that the RVs caused large-scale corrugations in the separation and reattachment lines. Furthermore, footprints of small tornado-like vortices could also be seen along the device centrelines, which were likely formed due to interactions between the streamwise vortices and the separation bubble.