Corner effect and separation in transonic channel flows

An investigation into parameters affecting separation in normal shock wave/boundary layer interactions (SBLIs) has been conducted. It has been shown that the effective aspect ratio of an experimental facility (defined as δ*/tunnel width) is a critical factor in determining when shock-induced separation will occur. Experiments examining M ∞ = 1.4 and 1.5 normal shock waves in a wind tunnel with a small rectangular cross-section have been performed and show that a link exists between the extent of shock-induced separation on the tunnel centre-line and the size of corner-flow separations. In tests where the corner-flows were modified ahead of the shock (through suction and vortex generators), the extent of separation around the tunnel centre-line was seen to vary significantly. These observations are attributed to the way corner flows modify the three-dimensional shock-structure and the impact this has on the magnitude of the adverse pressure gradient experienced by the tunnel wall boundary layers.