Use of Sweeping Jets During Transient Deployment of a Control Surface

Unsteady aerodynamic loads were measured on a NACA 0021 airfoil during rapid flap deflections. Typical dynamic-stall effects like an overshoot in lift, drag, and pitching moment have been observed in the absence of active flow control. Final flap-deflection angles and the rate of their deflections were varied at a constant angle of attack. Stall prevention or delay was achieved by fluidic actuators that generated discrete sweeping jets over the upper surface of a deflected simple flap. Static experiments proved the effectiveness of these actuators in preventing flow separation, thus increasing the lift and decreasing the drag of the airfoil. Dynamic tests proved their efficacy in dynamic stall. A significant gain in lift and a substantial reduction in drag were achieved within a short time period, even when the flap deflection was high.