Experimental Study of Dynamic Stall Control Using Deployable Leading-Edge Vortex Generators

A new concept of active dynamic stall control is proposed, designed and experimentally tested on a OA209 airfoil model. The active control principle is based on leading-edge vortex generations in order to alleviate the dynamic stall vortex formed and convected at the leading-edge of the airfoil. The active device aims to be used only during retreating blade side for dynamic stall flight conditions in order to avoid drag penalties on the advancing blade side. The designed actuator is a row of deployable vortex generators (DVGs) located at the very leading-edge of the airfoil. When retracted the VG fits the airfoil shape. Deployment is possible for different heights as well as different phases and frequencies with respect to the airfoil oscillation. The paper addresses the validation of the efficiency of the devices to delay static stall and alleviate penalties of dynamic stall. Results show a delay in static stall angle of attack of 3 degrees and reduction of negative pitching moment peak up to 60% for dynamic stall. The analysis of the experimental database indicates that different compromises between lift and pitching-moment can be achieved in dynamic stall depending on the phase actuation of the DVGs. The paper presents also optimized deployment laws that allow improving the duty cycle of the DVGs actuation while keeping significant reduction of dynamic stall penalties.