The effect of small-scale roughness on the main flow profile of a laminar boundary layer

The processes by which distributed surface roughness accelerate boundary layer transition remain unclear. Experimental studies aimed at clarification were carried out during the early 1980s by three groups who maintained intercommunication. In each case, Blasius-like boundary layers were selected for study for reasons of simplicity and standardization. The experiments by Leventhal [1] and by Corke, Bar-Sever, and Morkovin [2] concerned measurement of the growth of naturally-occurring flow fluctuations within laminar layers during passage over sandpaper roughness. In contrast, this author [3] chose to measure only the mean velocity alteration due to roughness, with the expectation that the distorted profile could be analyzed for incremental growth using stability theory.