Boundary Layer Transition of Strongly Concave Surfaces

Abstract

Boundary layer transition has been studied on two blades of constant 0.5 and 1 metre radius of curvature with free stream turbulence levels of 0.7%, 2.6% and 7.2%. Zero pressure gradients were used throughout. Strong Gortler vortices developed in the boundary layer which led to growth rates of up to ten times the flat plate rate. The boundary layer profile was also highly distorted by the vortices. Transition correlation techniques for flat plates proved totally inadequate for the concave surface data, but a method of obtaining correlations for these surfaces was suggested by considering the inner critical region of the boundary layer alone.