TURBULENT BOUNDARY-LAYER FLOW OVER FIXED AERODYNAMICALLY ROUGH 2-DIMENSIONAL SINUSOIDAL WAVES

Results from a wind tunnel study of aerodynamically rough turbulent bo undary-layer flow over a sinusoidal surface are presented. The waves h ad a maximum slope (ak) of 0.5 and two surface roughnesses were used. For the relatively rough surface the flow separated in the wave trough s while for the relatively smooth surface it generally remained attach ed. Over the relatively smooth-surfaced waves an organized secondary f low developed, consisting of vortex pairs of a scale comparable to the boundary-layer depth and aligned with the mean flow. Large-eddy simul ation studies model the flows well and provide supporting evidence for the existence of this secondary flow.