Effect of Suction Side Jet on the Shock Wave Boundary Layer Interaction in Transonic Turbine

Abstract In this paper, the effect of round jet with inclination angle 135° upstream the throat on the suction surface on shock wave boundary-layer interaction was investigated in a transonic turbine cascade, and the vortical structures near the jet region were analyzed. Owing to locally high concave curvature on the pressure side profile, the double shock wave structure was obtained in the turbine passage near the pressure side trailing edge. The first incident shock does not induce the boundary layer separation. The second strong incident shock transmits from the trailing edge of the pressure side and reaches the suction side of the adjacent blade. Strong interaction between the suction side boundary layer and incident shock wave exists in this region, and the separation bubble appears in the no jet case. The complex shock wave system and corresponding flow characters are analyzed. Due to the complex vortical structures on the blade suction surface with suction side jet, the pressure distribution on the suction side changes, and the shock wave system in the transonic turbine passage is rearranged, thereby influencing the shock wave boundary layer interaction. The separation onset decays with the suction side jet, and it keeps move downstream with increasing jet velocity. Length of the separation bubble is significantly reduced with suction side jet. However, when the jet velocity is beyond a certain value, the effect of suction side jet will not improve. The complex vortical structures with suction side jet will reenergizing to the low momentum fluid within boundary layer, and the mean velocity profiles in the boundary layer near the shock wave boundary layer interaction religion with suction side jet are more solid than the no jet case, which infers stronger resistance to flow separation. Complicated vortical structures exist near jet region, the Kelvin–Helmholtz instabilities of the shear layer of the jet flow and its coherent structures dominate the unsteadiness of the suction surface. The incident shock wave enhances the pressure fluctuation in the SBLI region, whereas the effect concentrates only on the first harmonic of the K-H instability but not higher frequencies.