Review—Transition in Nonreversing Oscillating Boundary Layers

Abstract

Literature on transition in oscillating boundary layers is relatively recent and confusing. The paper first reviews the current thinking on transition in steady boundary layers and on the role of stability theory. The reader is then provided with a background on oscillating boundary layers. The various reports of transition in such boundary layers are analyzed and clarified. The concept of excited wave packets, moving downstream through the “pulsating” boundary layer and cumulatively growing or decaying, largely in response to the transient vorticity distribution, appears to unify much of the data. Recent experiments, designed to test the ingredients of the concept, are reported. Other forms of transition are discussed and their probable occurrence in the domains of interest to practical engineers is mapped out.