Fast pressure-sensitive paint measurements of dynamic stall on a pitching airfoil via intensity- and lifetime-based methods

This study investigated unsteady pressure measurements on a pitching OA309 airfoil at a Mach number of 0.1 using a fast-responding pressure-sensitive paint (fast PSP). Two commonly used data acquisition methods applicable to fast PSPs, namely the real-time intensity-based method and the single-shot lifetime-based method, were separately used to obtain the pressure distributions on the upper surface at a reduced pitching frequency (k = πfc/U_∞) of 0.074. The signal-to-noise ratio, influences of model motion, and temperature-induced errors associated with the two methods were compared to explore the advantages and disadvantages of the methods. The real-time intensity-based method outperformed the single-shot lifetime-based method in pressure measurements on moving models with very low speeds. Flow separation and reattachment were identified according to the temporal- and spatial-resolved pressure fields obtained through the real-time intensity-based method; finally, the effects of the pitching amplitude and the leading-edge vortex generators were studied. The results showed that flow separation was postponed as the pitching amplitude increased, while flow reattachment occurred earlier on the airfoil equipped with leading-edge vortex generators.