“Anomalous” nonlinear wave phenomena in a supersonic boundary layer

Nonlinear evolution of high-amplitude periodic disturbances in a boundary layer on a flat plate for Mach number $\mathrm{M}=2$ is studied. An anomalous downstream evolution of the disturbances is found, quasi-two-dimensional disturbances being most unstable. The obtained phase velocities of the waves are $30$ – $40\%$ greater than the phase velocities of the Tollmien–Schlichting waves. The nonlinear evolution of vortex waves is accompanied by an increase in steady disturbances from the source of controlled vibrations. High-frequency disturbances decay, and a periodic wave train degenerates downstream into a quasiharmonic wave train.