A turbulent flow over a curved hill. Part 1. Growth of an internal boundary layer.

Discusses two experiments on the response of turbulent boundary layers to sudden changes in surface curvature and pressure gradient. In the first, the behaviour of a boundary layer over a two dimensional hill was studied. In the second, the flow over a symmetrical wing was studied, the wing having the same profile as the hill with similar pressure distribution. Describes experimental set up in the large closed return wind tunnel used. Presents results for skin friction distribution, and integral parameters. Compares wing and hill flow. Similarities are observed in the skin friction coefficients, and wake factors differ only slightly. Momentum thickness Reynolds numbers differ widely. Results indicate that an internal layer forms in the flow over a curved hill and that this internal layer is rather like the boundary layer observed on the free wing. In the hill flow the knee points in the Reynolds stress profiles appear as soon as the logarithmic region recovers over the convex surface. Discusses the perturbation responsible for the internal boundary layer. Compares results qualitatively with meteorological studies of flow over hills. (C.J.U.)