Experiments on the influence of surface curvature upon the development of streamwise vortices in an unstable three-dimensional boundary-layer flow.

Abstract

The development of streamwise vortices and transition of the three-dimensional boundary layer flow on a curved surface is studied experimentally. The model is a cylindrical wing shaped body with concave and convex profile segments. It is set at a sweep angle of 30 degrees. In order to enable comparison with theory quasi two-dimensional flow conditions are approximated by means of countured end plates. The streamwise pressure gradient leads to the amplification of both Goertler and crossflow instabilities. The disturbance development is measured by means of hot-wire anemometry. Surface hot-films are used for tracing transition. Streamwise vortices are found to be strongly amplified along the concave segment in the presence of strong and weak crossflow as well. No characteristic difference is found for the streamwise vortices developing in the two cases.