Near-normal shock interaction with turbulent boundary layer

Because the turbulent boundary layer is far less susceptible to disturbance by an adverse pressure gradient than is a laminar one, separation is not Ukely to occur for local mainstream Mach numbers, ahead of the shock, of less than about 1.3 (this corresponds to a downstream-to-upstream pressure ratio of about 1.8). When no separation occurs, the thickening of the boundary layer ahead of the shock is rapid and the compression wavelets near the base of the main shock are very localized, so that the base of the shock appears to be slightly diffused, although no lambda formation is apparent. Behind the shock no subsequent thinning of the boundary layer appears to occur and the secondary shocks, typical of laminar boundary-layer interaction, do not develop.

If separation of the turbulent layer occurs ahead of the main shock a lambda shock develops and the mainstream flow looks much like that for a fully separated laminar boundary layer.