Development of Localized Disturbances from an Oscillating Point Source in Compressible Boundary Layers

Abstract

Development of localized disturbances generated by an oscillating point source in compressible boundary layers with a zero pressure gradient at Mach numbers from 0.2 to 2.0 is studied theoretically on the basis of the linear stability theory. The method of complex characteristics recently proposed by Itoh as an extension of Whitham’s kinematic wave theory, is applied to describe wave propagation from the oscillating source. The analysis demonstrates distinct differences in the development of localized disturbances between the subsonic and supersonic boundary layers. Importantly, maximum growth occurs away from the midspan in supersonic boundary layers, while it occurs at the midspan in subsonic boundary layers.