Leading edge vortex control on a delta wing with dielectric barrier discharge actuators

Abstract

The interest in the active flow control based on dielectric barrier discharge (DBD) plasma actuators has increased rapidly in the past decade. Because of its features such as light weight, low power consumption, fast response and flexibility, the DBD plasma actuator is a promising technology in advancing the aerodynamic performance and maneuvering of unmanned aerial vehicles. In this study, DBD plasma actuators are employed on a full span delta wing with a 75 degree swept angle to control the leading edge vortices (LEV), which generate the vortex lift on the delta wing. The experiment is conducted in a low speed closed-loop wind tunnel and the Reynolds number based on the delta wing chord is 50,000. To fix the stagnation points, both leading edges are beveled on the windward sides at an angle of 35 degrees and actuators are insulated at the leading edges. These actuators are driven independently at a frequency of 20 kHz and a voltage of 12 kV in both continuous mode and periodic mode. The DBD actuators are calibrated using a pitot tube. Smoke flow visualization result indicates that the breakdown points of leading edge vortices can be significantly affected by DBD plasma actuators at the leading edge. In the asymmetric control case (only an actuator on one side is powered), the breakdown point of the LEV on the controlled side is greatly advanced while the one on the uncontrolled side is delayed; in the symmetric control case (actuators on both sides are powered), the control shifted the breakdown points of both LEVs further downstream. Particle image velocimetry (PIV) demonstrates clearly that the control caused by DBD actuators at the leading edge can influence the separation at the leading edges and also the shear layer vortices, which form the substructures around the primary vortices. As a result, breakdown points of LEVs are affected. Interestingly observed, the control leads to a contrary flow phenomenon: in the asymmetric case, the breakdown point of the LEV on the controlled side is advanced while, in the symmetric control case, the breakdown points of the LEV on both sides are delayed. The effects of reduced frequency and duty cycle on the control authority are also investigated experimentally. Control efficiencies of both continuous mode and periodic mode are discussed.