Structure and mean flow similarity in curved turbulent boundary layers

Abstract

Experiments have been conducted on turbulent boundary layers with a curvature parameter (i.e., the product of the curvature and the initial boundary layer thickness) ranging from −0.078 (concave) to +0.124 (convex). Measurements with an array of hot wires and a surface hot-film gauge on the organized structure in the boundary layer, and on Reynolds stress distributions, suggest that curvature loosens the coupling between wall and outer flows, on both convex and concave walls (although for different reasons). This is confirmed by the finding that the outer defect law is independent of the friction velocity. New similarity laws for the mean velocity distribution are proposed on this basis.