Transition Movement in the Wake of Protruding and Recessed Three-Dimensional Surface Irregularities

Abstract

A study is conducted to investigate the initial movement of transition downstream of protruding and recessed surface irregularities. Experimental data is provided on the transition movement, and on the steady and unsteady boundarylayer characteristics leading to the transition movement. The transition Reynolds numbers collapse reasonable well when plotted in terms of the roughness height non-dimensionalized by the boundary-layer displacement thickness. Local stability analysis is shown to capture many of the features of the pre-transitional flow. The upstream movement of the transition can be represented by a reduction in the critical N-factor, similar to earlier studies on surface roughness or two-dimensional steps.