Abstract
Dielectric barrier discharge (DBD) plasma actuation has been widely recognized as an effective active flow control method on aircraft or wind turbines due to its unique advantage of rapid momentum transport through an induced airflow by the acceleration of ionized gas during plasma discharge. Applications include lift augmentation on wing sections, manipulation of turbulent boundary layers, and leading-edge separation flow control, among others. However, airplane or wind turbine surfaces where DBD plasma actuators are installed are consistently exposed to humid environments or droplet clouds. Under these conditions, water droplets can impact the plasma actuators and interact with the plasma discharge. In this paper, the dynamic processes of water droplets impacting on the plasma discharge region of a surface DBD actuator were studied. A series of thermal-flow diagnostic methods, including High-speed imaging, infrared thermal imaging, and Schlieren visualization, were utilized to characterize the dynamics of droplet impacting and interacting with a surface DBD plasma discharge. It is found that the droplet initially acts as an extended electrode, it then migrates in the direction of induced flow and promotes the formation of high-intensity plasma streamers. It is also revealed that there is a significant increase in the angle (from ∼ 14° to ∼ 44°) of the induced airflow within the first 30 ms after droplet impact. The dominating airflow structures were characterized using high-speed imaging. The changes in flow direction and momentum flow rate found in this study are expected to fundamentally alter the performance of DBD actuators.
