Abstract
Effects of upstream disturbances on transition of a supersonic boundary layer over an adiabatic flat plate at Mach 2.0 are investigated by means of direct numerical simulation. Spatially evolving transitional flows are analyzed to study the differences of transition process and resultant flow structures due to different dynamics of the disturbances (a first mode oblique wave, wide region random and spot-like disturbances). Simulated flows indicate that streaks and longitudinal vortices are generated as the amplified oblique waves travel downstream. Low-speed streaks, quasi-longitudinal vortices and hairpin vortices are generated in the supersonic boundary layer due to high wide region disturbances bypassing the wave amplification, which closely resembles the incompressible flow. The flows due to the local-disturbances show transient growth flow patterns downstream leading streaks inflectional instability.
