Disturbances Growth in Boundary Layers on Classical and Wavy Surface Wings

Oil-film visualization patterns of the flow on a classical wing and on a wing with a wavy surface at various angles of attack are analyzed. For low Reynolds numbers (Re < 2 10 5 ), the boundary-layer structure on a wavy wing is demonstrated to differ significantly from that on a classical wing. As result, leading-edge stall on a wavy wing occurs later than on a smooth wing. The present activities form the basis for a systematic study of the boundary-layer structure on a wavy wing. For this purpose, a series of investigations is performed. Boundary-layer parameters on classical and wavy-surface wings at the angle of attack α= Odeg and the chord Reynolds numberRe = 1.7 x 10 5 are studied experimentally. The combined experiment includes oil-film visualization, measurements of pressure distributions, and flow velocity. On both wings, substantial differences are found in the transition position and in the transition scenarios realized on the wavy-surface wing along its streamwise grooves and humps. However, some similarity in the disturbance growth in both separation-bubble regions is found.