Experimental investigation of the shock wave/boundary layer interaction at a compression corner and an incident shock wave generator

Abstract

The separation of the boundary layer is one of the main failures in scramjets due to its influence on the amount of oxygen used in combustion, reducing thrust and specific impulse. The main objective of this paper was to perfom experimental investigations to study the shock wave/boundary layer interaction and boundary layer separation. The experimental investigation was done in the T2 shock tunnel using the throats/nozzles for theoretical Mach numbers of 6.5 and 8.3. Compression ramp (30° and 20°) models made of aluminum and printed on plastic filament in the 3D printer were designed and produced, as well as two shock generators models with 30°. The flow analysis was performed using pressure sensors and the schlieren image technique. In the cases of shock generators, the incident shock wave caused an increase in pressure and reached a plateau inside the separation bubble (from 81.84 kPa to 360.01 kPa). The highest pressure values were related to the reattachment line. Then, the expansion waves cause a reduction in pressure and adjacent phenomena cause increase in pressure. The ramps caused an increase in pressure and an effect close to a plateau. Then, the boundary layer is replaced and the pressure continues to increase until the end of the ramp, obtaining values from 15.9 kPa to 93.8 kPa. The highest pressure values were observed in the region of interaction of the incident shock wave with the reattachment shock. The pressure values between the aluminum and plastic filament models measured different values along the ramp (45.6 kPa and 28.8 kPa) in the last sensor. The images in schlieren were of excellent quality and the technique was highly efficient to visualize the phenomena. As results of these campaigns, it was possible to visualize the adverse pressure gradient, the flow separation structure, including the separation bubble and reattachment of the boundary layer.