An Experimental Investigation of Dynamic Stall Control with a Leading-Edge Microcavity Actuator

The effectiveness of a micro-cavity near the leading-edge of sinusoidally pitching NACA 0012 airfoil is experimentally investigated as a means of dynamic stall control. The micro-cavity is sized and positioned to excite resonant oscillations during deep stall and thus collapse the leading-edge separation bubble. Wind tunnel testing focused on freestream conditions of M = 0.20 – 0.25, Re = 6.8 – 8.35 x 〖10〗^5, and reduced frequency, k = 0.039 - 0.049. Micro-cavity results at M = 0.20 and 0.25 showed improved lift, reduced hysteresis, and earlier downstroke flow reattachment relative to the uncontrolled airfoil. Normal and axial force contours revealed the presence of intermittent pitching cycles of beneficial control, which were increasingly present in the downstroke portions of M = 0.25 flow. These events, which are indicative of effective micro-cavity control, were separated and conditionally averaged to reveal significant (up to 56%) reductions in hysteresis and a transition from negative to positive aerodynamic damping. This study offers the first experimental verification of the micro-cavity actuator for dynamic stall control.