Plasma Behavior and Temporal Flow Velocity in AC Plasma Actuator

Summary form only given. Plasma actuators can induce a gas flow of several m/sec in the downstream of electrodes in atmospheric conditions. In a AC plasma actuator driven by a dielectric surface barrier discharge, peak values of micro-discharge current, plasma shapes and temporal flow velocity change according to the polarity of the applied voltage. A temporal velocity measurement was reported using a laser Doppler velocimeter, but a driven mechanism of the flow is not well understood. In our experimental setup, two metal electrodes are attached asymmetrically on both sides of a glass plate of 3 mm in thickness. A grounded electrode is exposed to the surrounding air and a high voltage electrode is buried in an acrylic board. By applying sinusoidal voltage of 35 kV_pp and 2 kHz between the electrodes, surface barrier discharges are generated over the glass surface and a unidirectional gas flow is generated. Relatively large discharge currents are observed when the polarity of the applied voltage is changed from positive to negative (: negative-going cycle) and such current pulses last until the voltage reaches the negative peak. High-speed photographs taken by an ICCD camera in the exposure time of 25 musec show that many contracted plasma channels are generated in this cycle. However, no large pulsed currents are measured during the positive-going cycle and almost uniform discharges are observed over the glass plate. The flow velocity around the plasma is measured at a time interval of 62.5 musec. The flow velocity is few m/sec in the downstream of the plasma but fluctuates at the frequency of 2 kHz above the plasma. The maximum and minimum values of the flow velocity are observed around the positive and negative peaks of the applied voltage, respectively. These fluctuations of the flow velocity seem to be caused by the electric field but a primary factor is unsolved.