The effect of concave surface curvature on turbulent boundary layers

Abstract

The response of a turbulent boundary layer to suddenly applied concave surface curvature with δ/R = 0.01–0.02 is investigated. The main conclusion of this and the companion paper by Muck, Hoffmann & Bradshaw (1985) is that the effects of concave (destabilizing) and convex (stabilizing) curvature on boundary layers – and presumably on other shear layers – are totally different, even qualitatively. As shown in Muck, Hoffmann & Bradshaw (1985), convex curvature tends to attenuate the pre-existing turbulence and, at least in the case of mild curvature, there are no large changes in statistical average eddy shape. Concave curvature, on the other hand, can lead to the quasi-inviscid generation of longitudinal (‘Taylor–Gortler’) vortices, and we show that significant changes in the turbulence structure are induced both directly by the curvature and indirectly by the vortices.