Static and dynamic stall control by NS SDBD actuators

In the last two decades, nonequilibrium plasmas have demonstrated the ability to affect a variety of flows of aeronautical interest, including mitigation of stall on steady airfoils as it is a nonintrusive, active control method. Plasma actuation also shows promise to address dynamic stall in rotorcraft because of the absence of moving parts, extremely lightweight and flexible assembly, extremely fast turn-on time and wide range of actuation frequency. In this paper, we summarize the recent advances in flow control both for static and dynamic flow separation control using nanosecond pulsed surface dielectric barrier discharge plasma devices. Topics of discussion include the mechanism of NS plasma actuation, results of experiments at different Reynolds and Mach numbers, dynamics of flow reattachment, and boundary layer separation control on a pitching airfoil. The common issue of retreating blade stall, as experienced in helicopters, was also considered in this study by experimenting with a reverse flow over an airfoil. Increases in lift are demonstrated for separated flows for reduced frequencies up to k = 0.05, angle of attack up to 32°. Instantaneous increase in lift with plasma control was demonstrated to be up to 55%. The 20% integral lift force increase of a helicopter model in hover mode using a constant engine power is also demonstrated with NS SDBD actuation of the flow on the rotating blades. (paper)