Stability limits and transition times of wave-induced wall boundary layers

The study concerns theoretical analysis of stability and experimental investigation of transition for laminar wall boundary layers developed within plane expansion waves and behind shock waves traveling into gas at rest. The stability analyses involved approximate methods for critical stability Reynolds numbers, numerical integration of the Orr-Sommerfeld equation, and a multiple-scales perturbation technique for unsteady boundary layers. In the experiments several techniques were used to detect transition. Expansion-wave transition times measured are typically five times larger than reported by previous investigators. Shock-wave transition times are generally in close agreement with previous results. Most of the transition times are less than critical stability values from linear theory.