Investigation of Three-dimensional Dynamic Stall on an Airfoil using Fast Response Pressure Sensitive Paint

Dynamic stall on a pitching OA209 airfoil in a wind tunnel is investigated at Mach 0.3 and 0.5 using high-speed pressure sensitive paint (PSP) and pressure measurements. At Mach 0.3 the dynamic stall vortex was observed to propagate faster at the airfoil midline than at the wind tunnel wall, resulting in a "bowed" vortex shape. At Mach 0.5 shock-induced stall was observed, with initial separation under the shock foot and subsequent expansion of the separated region upstream, downstream and along the breadth of the airfoil. No dynamic stall vortex could be observed at Mach 0.5. The investigation of flow control by blowing showed the potential advantages of PSP over pressure transducers for a complex three-dimensional flow.