Control of the dynamic stall process of an NACA 0015 airfoil undergoing periodic pitching motion is investigated experimentally in a high-speed wind tunnel facility. Multiple microjet nozzles distributed uniformly in the first 15% chord from the airfoil’s leading edge are used for the control. Point Diffraction Interferometry (PDI) technique is used to characterize the control effectiveness, both qualitatively and quantitatively. The microjet control has been found to be very effective in suppressing both the emergence of the dynamic stall vortex and the associated massive flow separation at the entire operating range of angles of attack. At the high Mach number case (M = 0.4), the use of microjets appears to eliminate the shock structures that are responsible for triggering the shock-induced separation, establishing the fact that the use of microjets is effective even in controlling dynamic stall with a strong compressibility effect. In general, microjet jet control has an overall positive effect in terms of maintaining leading edge suction pressure and preventing flow separation.

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