Corner effects for compression corner shock wave/boundary layer interactions in rectangular channels

A 20 deg compression corner is used to establish a separated oblique shock wave/turbulent boundary layer interaction in a rectangular cross-sectioned wind tunnel with an incoming Mach number of 2.5. An experimental investigation is conducted to establish the influence of separation in the streamwise corners, formed by the intersection of the working-section floor and side walls, on the quasi two-dimensional main interaction and by what mechanism the two regions interact. To investigate this, the streamwise location and size of the corner separations are manipulated and the flowfield is studied using schlieren photography, oil-flow visualisations, pressure sensitive paint, and laser Doppler velocimetry measurements. The results indicate that the size and structure of the primary separation can vary considerably with different streamwise locations of corner separation. Three regimes of corner effects are identified with respect to the primary separation length; a regimes of enhanced streamwise separation length, decreased separation length, and quasi two-dimensional separation. Compression waves and expansion fans generated as a result of the displacement effect of the corner separations appear to be the primary mechanism behind the observed behaviour. These waves propagate from the corner regions and impinge on the primary interaction, modifying the pressure rise and adverse pressure gradient.