Mechanism of shock-train/boundary-layer interaction in spanwise concave isolator channels

Abstract

A series of spanwise concave channel models of isolators with different radii were investigated to reveal the mechanism of shock train/boundary layer interaction in the inward-turning inlet. Numerical simulations of the shock train flow under different incoming Mach numbers, incoming static pressures, and backpressure ratios were performed. The results show that the shock train leading edge exhibits a “λ” shape in the concave channel, and that a Mach stem is present at the intersection of the shock waves on the top and bottom walls. As the radius of the concave wall is increased, the streamwise force generated by the wall decreases and the upward force perpendicular to the wall increases, which leads to an increase in the thickness of the boundary layer and weakening of the ability of the boundary layer fluid to resist the pressure gradient. Owing to the increase in the radius of the concave channel, the shock train moves upstream, the Mach stem in the shock train leading edge becomes shorter, the distance between the reflection shock waves increases, and the shock train becomes longer. Compared with the concave bottom wall, the separation flow at the flat top wall extends further streamwise. As the incoming Mach number increases, the inertial effect is strengthened, and the shock train evolves towards a normal shock wave structure. As the incoming static pressure decreases, the viscous effect is enhanced, and the flow field of the shock train tends to evolve to reflect more shock waves with compression over longer streamwise distances.