Influence of compressibility on three-dimensional boundary layer stability

Stability of compressible three-dimensional boundary layers is examined on the basis of the linearized stability theory. The stability analyses are ma de for subsonic and supersonic boundary layers mainly at Mach numbers of ex ternal flow, M-e=0.2 and 2.0, by using a family of the Falkner-Skan-Cooke p rofiles as the base flaws. The results clearly show that the cross-flow ins tability becomes completely dominant when the magnitude of the cross-flow v elocity exceeds about 4% of the external flow velocity, both at the subsoni c and supersonic Mach numbers over a wide range of Reynolds numbers. It is also shown that the influence of compressibility on stability characteristi cs such as the propagation angle and growth rate of the most amplified firs t mode is weak for cross-how instability.