Reattaching Flow Behind a Forward-Backward Facing Step Investigated with Temperature-Sensitive Paint

Abstract

The flow features developing in the presence of a two-dimensional forward-backward facing step of small width are visualized. The flow visualizations were conducted by means of Temperature-Sensitive Paint (TSP). The tests were conducted in the Laminarwasserkanal (laminar water channel) at the Institute for Aerodynamics and Gas dynamics (IAG) in Stuttgart. A step Reynolds number Re k from 199 up to 1890 enables the investigation of laminar, transitional and turbulent reattachment of the flow. The variations of flow separation and impinging structures related to reattachment are well captured by the TSP technique. The TSP method requires a temperature difference between the model surface and the flow to visualize flow phenomena. This temperature difference alters the flow structures around the forward-backward facing step for low Reynolds numbers by inducing buoyancy forces in the boundary layer and recirculation zone.