Duct Height Effect on Terminal Shock/Boundary-Layer Interaction in a Generic Supersonic Inlet

Abstract

A generic external-compression inlet model was tested to investigate the effect of duct height on terminal shock/boundary-layer interactions, with special sidewall arrangements to eliminate corner separations. Experimental results showed that the separation length significantly decreased by 41% as the duct height was reduced from 60 mm [Formula: see text] to 40 mm [Formula: see text]. To obtain the influence of the duct height in a wider range of values, Reynolds-averaged Navier–Stokes simulations were further performed. The scales of the [Formula: see text]-shock structure and separation region decrease as the duct height decreases. Shrinkage of the scale of the λ-shock structure results from a decrease in separation length. The downstream shift in the separation point and the upstream shift in the reattachment point both contribute to this decrease, but the upstream shift in the reattachment point is a dominant reason. The underlying mechanisms of the variation in the reattachment position as the duct height decreases include two aspects. The first is the stronger pressure gradient in the wall-normal direction immediately behind the shock system, which produces a stronger radial pressure gradient above the bumplike separation bubble, quickly turning the streamlines toward the bottom wall and enclosing the bubble. The second results from the postshock acceleration of the irrotational flow above the separated layer as the duct height decreases. An accelerating mainstream with a favorable pressure gradient above the separated layer increases the mixing strength and momentum exchange between the low-speed layer near the wall and high-speed flow above the separated layer.