Dielectric Barrier Discharge Plasma Actuators for In-Flight Transition Delay

A single dielectric barrier discharge plasma actuator is employed for flow control on the pressure side of a natural laminar flow wing section under free-flight conditions. A full-sized motorized glider is equipped with the flow-control device and data-acquisition hardware to quantify the impact of the actuator on boundary-layer transition. A transition delay of approximately 3% chord is achieved, quantified by microphone and hot-wire measurements. Simultaneously, the influence of the variable ambient conditions on the flow-control performance is characterized. A closed-loop control algorithm enables constant actuator performance, despite varying humidity, temperature, and density throughout the test flights. The energy efficiency of the flow-control approach is estimated, providing a positive outlook for further improvements and a net benefit of transition control. Finally, a numerical procedure is presented to quantitatively estimate the effect of dielectric barrier discharge actuation on boundary-layer transition to enhance the design of flow-control experiments.