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 generation in order to alleviate the dynamic stall vortex formed and convected at the leading-edge of an airfoil operating at a helicopter blade in fast forward flight. 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 leading-edge of the airfoil that fit the airfoil shape when retracted. 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 effectiveness of the devices to delay static stall and alleviate dynamic stall penalties. Results show a delay in static stall angle of attack of 3 deg and a 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 depending on the phase actuation of the DVGs.