The glancing interaction of a Prandtl-Meyer expansion fan with a supersonic wake is examined. The particular supersonic wakes of interest are the combustion wake generated by a vertical strut injected scramjet, and the side wall boundary layer of a supersonic wind tunnel. A physical structure for the interaction is defined, and an approximate analysis of the downstream behaviour of the wake is presented. The phenomenon of wake over-turning by the glancing expansion fan is introduced, based on this analysis. This over-turning produces a high pressure zone on the expansion generating surface, which for the vertical strut injected scramjet, is part of the thrust nozzle. Combustion wake over-turning is suggested to be a major thrust producing mechanism in this form of scramjet.
Pressure measurements were taken on the expansion generating surface of a glancing interaction involving the side wall boundary layer of a small supersonic wind tunnel. Results from the analysis presented were found to be consistent with these measurements.