Transition Delay by Oblique Surface Roughness

Kurzfassung

The laminar-turbulent Transition caused by Tollmien-Schlichting waves can be delay by introducing streaks of appropriate strength into the laminar boundary layer. lt has been shown numerically and experimentally that roughness elements can generate stable streaks of sufficient strength. The roughness elements tested so far have a wake of counter-rotating vortices. In the current work a different roughness type, i.e. an oblique surface roughness, with a wake of co-rotating vortices was successfully used to delay transition in the Laminarwasserkanal of the Institute of Aerodynamics and Gas Dynamics, University Stuttgart. The conditions of the transition were weil controlled and the temperature-sensitive paint (TSP) method and hot-film anemometry were used to investigate the flow.