Ramped Vane Control of a Compression Corner-Induced Flow Separation

Abstract

A numerical study was conducted to determine the ability of ‘Ramped Vane (RV)’ type vortex generators in mitigating the shock-induced flow separation formed in the vicinity of a planar compression corner. The incoming freestream flow was at Mach 2 and the ramp angle was 24°. The RVs were placed 50 mm upstream of the corner, where the local boundary layer thickness (δRV) was 3.5 mm. The devices were completely submerged within the boundary layer and were 2 mm (h = 0.57δRV) and 2.5 mm (h = 0.71δRV) tall. Strong streamwise counter-rotating vortices were produced by the RVs, which replaced the low-momentum fluid in the near-wall region with high-momentum fluid from the outer parts of the boundary layer. As a result, the boundary layer was able to push through the adverse pressure gradient to a greater extent, delaying the onset of flow separation. The larger RVs exhibited superior separation control performance, as the vortices originating from these devices lifted off at a relatively rapid pace and thus were able to remove the low momentum fluid more quickly from the near-wall region. Additionally, the surface flow patterns showed conspicuous spade-shaped patterns ahead of the compression corner, which are likely the footprints of tornado-like vortices formed due to the interaction between the streamwise vortices and the main separation bubble. The paper also presents a detailed analysis of these topological alterations using the critical point theory.