SPATIAL 3-DIMENSIONAL SECONDARY INSTABILITY OF COMPRESSIBLE BOUNDARY-LAYER FLOWS

Three-dimensional linear secondary instability theory is extended for compressible and high-Mach-number boundary-layer flows. The effect of a small- but finite-amplitude compressible Tollmien-Schlichting wave on the growth of three-dimensional perturbations is investigated. The focus is on principal parametric resonance responsible for the strong growth of subharmonics in a low-disturbance environment. The effect of increasing Mach number on the onset, growth, and shape of eigenfunctions of the subharmonics is assessed, and the resulting vortical structure is examined.