Development of plasma actuators for high-speed flow control based on nanosecond repetitively pulsed dielectric barrier discharges

2019-06-10T16:34:53Z (GMT) by Aarthi Devarajan
Over the past few decades, surface dielectric barrier discharge (SDBD) actuators have been studied extensively as aerodynamic flow control devices. There has been extensive research on producing SDBD plasmas through excitation by sinusoidal high voltage in low-speed flows, resulting in local acceleration of the flow through the electrohydrodynamic (EHD) effect. However, high-speed flow control using SDBD actuators has not been considered to the same extent. Control through thermal perturbations appears more promising than using EHD effects. SDBDs driven by nanosecond repetitively pulsed (NRP) discharges (NRP SDBDs) can produce rapid localized heating and have been used to produce better flow reattachment in high-speed flows. While surface actuators based on NRP DBDs appear promising for high-speed flow control, the physics underlying the plasma/flow coupling are not well understood and the actuators have yet to be fully characterized or optimized. In particular, methods for tailoring the plasma characteristics by varying the actuator’s electrical or geometrical characteristics have not been thoroughly explored.
In the current work, NRP SDBD actuators for control of high-speed flows are developed and characterized. As discussed previously, it is believed that the mechanism for high-speed flow control by these plasmas is thermal perturbations from rapid localized heating. Therefore, the goal is to design actuators that produce well-defined filamentary discharges which provide controlled local heating. The electrical parameters (pulse duration, PRF, and polarity) and electrode geometries are varied and the optimal configurations for producing such plasma filaments over a range of ambient pressures are identified. In particular, single and double sawtooth shaped electrodes are investigated since the enhanced electric field at the electrode tips may permit easier production of “strong” (i.e. higher temperature) filaments with well-defined spacing, even at low pressure. Time-resolved measurements of the gas temperature in the plasma will be obtained using optical emission spectroscopy (OES) to assess the thermal perturbations produced by the actuators. To the author’s knowledge, these will be the first such measurements of temperature perturbations induced by NRP SDBDs. The plasma structure and temperature measurements will be correlated with schlieren visualization of the shock waves and localized flow field induced by the discharges. Finally, the optimized actuators will be integrated into a high-speed flat plate boundary layer and preliminary assessment of the effect of the plasma on the boundary layer will be conducted.