An Approach to Measuring the Effects of Surface Steps on Transition Using a Propelled-Model

An experimental study was undertaken to determine the effects of step excrescences on boundary layer transition using a unique ground test facility in which the test model was propelled though still air. The study made use of a model with infinitely adjustable step sizes and a single measurement surface for all cases. The test conditions examined and measurements made built on earlier work conducted in a low speed wind tunnel to measure the influences of pressure gradient on the relation between surface excrescences and boundary layer transition. The initial experience with propelled-model testing indicated that this approach is capable of providing a low disturbance test environment with Reynolds numbers representative of flight conditions.