Effects of Concave Curvature on Boundary Layer Transition Under High Freestream Turbulence Conditions

Abstract

An experimental investigation has been carried out on a transitional boundary layer subject to high (initially 9%) freestream turbulence, strong acceleration (K=(ν/Uw2)(dUw/dx) as high as 9×10−6), and strong concave curvature (boundary layer thickness between 2% and 5% of the wall radius of curvature). Mean and fluctuating velocity as well as turbulent shear stress are documented and compared to results from equivalent cases on a flat wall and a wall with milder concave curvature. The data show that curvature does have a significant effect, moving the transition location upstream, increasing turbulent transport, and causing skin friction to rise by as much as 40%. Conditional sampling results are presented which show that the curvature effect is present in both the turbulent and nonturbulent zones of the transitional flow.