Active Flow Control of a High-Lift Supercritical Airfoil with Microjet Actuators

摘要

Active flow control has the potential for substantial performance gains and meeting the challenges of next-generation air vehicles. High-lift airfoils employ trailing edge flaps during takeoff and landing, which are stowed during cruise. The present experimental investigation was carried out to examine the active flow control effectiveness on the NASA Energy Efficient Transport airfoil fitted with a simple hinged flap. Experiments were carried out at two flap deflection angles of 20 and 30 degrees at a Reynolds number based on aerodynamic chord of 3.4x105. The microjet parameters varied during this study were the location, orientation, and blowing ratio of the jets. Measurements include velocity and vorticity fields obtained using planar and stereoscopic particle image velocimetry. The baseline flow is separated over a third of the flap at a deflection angle of 20 degrees, and over the entire flap at a deflection angle of 30 degrees. Microjet control is able to completely re-attach the flow at both flap deflection angles and significantly reduce the airfoil drag. The mechanism for control effectiveness is the re-energizing of the boundary layer through the development of counter-rotating vortex pairs.