Influence of Expansion Waves on Cowl Shock/Boundary Layer Interaction in Hypersonic Inlets

Abstract

The cowl shock/boundary layer interaction is of great importance to the performance and operability of hypersonic inlets. However, it is usually affected by the expansion waves originated from the convex corner of the ramp surface (often called the shoulder), making the commonly used separation prediction relation unreliable. Therefore, the cowl shock/boundary layer interaction under the interference of the expansion waves is investigated by both theoretical analysis method and computational method in this paper. The results show that the expansion waves bring significant influence on the cowl shock/boundary layer interaction and four kinds of interaction processes exist when their relative position changes. When different interaction processes dominates the flowfield, the expansion waves may bring positive or negative effects on the shock/boundary layer interaction. In particular, while the cowl shock impinges near the shoulder, the interaction processes of shock-shock-expansion wave and shock-expansion waveshock bring positive effects on the shock/boundary layer interaction and suppress the boundary layer separation. Nomenclature d = distance between the shock impingement point and the shoulder d 1 = distance between the shoulder and the first demarcation point of the cowl shock/boundary layer interaction d 2 = distance between the shoulder and the second demarcation point of the cowl shock/boundary layer interaction h = height of the isolator M 0 = upstream Mach number M 1 = Mach number at the duct entrance M 3 = Mach number at the flow region downstream from the corner expansion fan and upstream from the cowl shock p sep = minimum pressure downstream of the shock when the boundary layer separation occurs p sh = pressure downstream of the incident shock p 0 = static pressure of the coming flow x = X-axis coordinate α = angle between the bottom wall of the duct and the cowl shock downstream from the expansion waves β = cowl contracting angle β 0 = angle of the shock generator δ = thickness of the boundary layer δ 0 = thickness of the boundary layer at the shoulder δ = displacement thickness of the boundary layer θ = momentum thickness of the boundary layer φ = ramp angle

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“…(3) here are similar to that in Zhang's paper. 12 The parameters in right hand sides of the Eq. (1) -(3) can be obtained directly except α.…”