Quantitative flow visualization of a turboprop aircraft by robotic volumetric velocimetry

The flow field around a turboprop aircraft scaled model is investigated with attention to the propeller slipstream and the wing near wake. The experiments are conducted in the Low-Speed Tunnel (LST) of the German-Dutch Wind Tunnels (DNW) as part of a collaboration among DNW, Delft University of Technology and Airbus. Quantitative flow visualization in a three-dimensional measurement domain of 150 liters is made possible by the use of the recently developed Robotic Volumetric Velocimetry technique. Time averaged velocity and vorticity fields are obtained for experiments carried out at 8 m/s and 50 m/s, respectively. The measurements are conducted with high-speed acquisition in multi-frame mode at 8 m/s, and require double-frame mode at 50 m/s. The presence of three coherent streamwise vortices is revealed, emanating from the wing tip, the flap side edge and the engine nacelle, respectively. A comparison between the two measurement conditions shows limited Reynolds number effects on the wing tip vortex, and that the multi-frame measurements are superior in terms of spatial resolution and measurement accuracy.