Interaction of a turbulent boundary layer with a normal shock wave followed by an adverse pressure gradient

An experimental study was made of the development of a turbulent boundary layer after an interaction with a normal shock wave (strong enough to cause a local separation) in a strong adverse pressure gradient. This type of flow, which occurs in air breathing engine components, is poorly understood and cannot be satisfactorily predicted. The measurements, made in a closed duct, extended well downstream of the shock wave interaction. Detailed results for the flow are presented and used to support two major conclusions. First it is shown that the post shock adverse pressure gradient has a large effect on boundary layer development through the interaction and downstream of it. Consequently existing results for interactions without a post shock pressure gradient should not be used as a model for practical flows which typically have strong pressure gradients applied downstream of the shock wave. The second conclusion was that the shock wave in a rectangular duct produced a pronounced stabilizing effect on the downstream flow. Surface flow visualization suggests that this stabilization is achieved by streamwise vortices shed into the flow from the separated region formed by the shock wave. The implication of this result to nominally two dimensional flow situations and to flows with weak interactions without local separations, is discussed.