Transition in the shock-induced unsteady boundary layer on a flat plate

The paper is concerned with transition in the unsteady boundary layer induced by the primary shock on a flat plate mounted in a shock tube. The times at which transition appeared at several thin-film heat-flux gage locations was determined for a range of initial test section pressures, and the data were applied to calculate displacement thickness Reynolds numbers for the laminar boundary layer at the observed transition points. The calculations show that the boundary layer is formed by the merging of the steady boundary layer that develops from the plate leading edge with a side-wall-like boundary layer that forms on the plate behind the advancing shock. The results are contrary to predictions based on amplification of Tollmien-Schlichting waves. It is suggested that the results can be applied to predict transition in a corresponding steady flow.