Propagation of disturbances in supersonic laminar and turbulent boundary layers

Disturbance propagation processes in supersonic laminar and turbulent boundary layers and in channels have been studied. Analysis of the corresponding subcharacteristics leads to an integral relation determining the velocity of disturbance propagation. The study of flows in a turbulent boundary layer described by a simple model leads to a conclusion that the upstream propagation of disturbances is possible only provided that the surface temperature (or the thickness of the region of a subsonic near-wall flow) is sufficiently large. For moderate surface temperatures, the upstream propagation of disturbances is restricted to distances comparable with the boundary layer thickness.