Design, Construction, and Validation of a New Wind Tunnel for the Study of Pressure-Driven Separating and Reattaching Flows

摘要

The design, construction, and validation of a new academic wind tunnel is described in detail. The wind tunnel is of a classical, blow-down type and generates a pressure-driven, turbulent separation bubble on a flat test surface. The Reynolds number, based on momentum thickness just upstream of separation, is Re_θ approx= 5000 at a free-stream velocity of U_(ref) = 25 m/s. The length of the separation bubble has been estimated at 0.42 ± 0.02 m by three different methods. Experimental and numerical results demonstrate the absence of flow separation in the wind-tunnel contraction. This results in a turbulence level of about 0.05% in the test section. Oil-film visualization experiments show that the flow near the wall is strongly three-dimensional in the recirculating region and that the topology of the limiting streamlines is consistent with experiments performed on configurations with fixed separation. Finally, spatial variations of the forward-flow fraction have been documented using a thermal-tuft probe and are shown to compare well with the results of the oil-film visualization.