On Plasma Synthetic Jet Actuators

The term plasma actuator refers to an asymmetric arrangement of two electrodes (typically rectangular strips) separated by dielectric material that can be used as active flow control devices. A plasma actuator design consisting of an annular electrode array, the plasma synthetic jet actuator (PSJA), is experimentally investigated in this paper. This particular geometry creates a zero-net mass flux (or “synthetic”) jet upon actuation, and can be operated in a pulsed or steady manner for flow control or thrust generation. Unlike synthetic jets, the actuator configuration can be reversed to act as a suction device. 2-D PIV measurements are used to characterize the actuator mounted on a flat plate in quiescent flow. Pulsing the actuator results in formation of three counter-rotating vortex rings: a starting vortex ring that advects downstream ahead of the jet, a secondary vortex ring that is found to be “trapped” during the actuation phase, and a weak strength tertiary vortex ring created as a result of fluid entrainment in the boundary layer. Examination over a range of frequencies reveals varying values of peak jet velocity and momentum distribution based upon interactions of the starting vortices. The effects of changing pulsing frequency on the jet characteristics are discussed. Preliminary observations on a PSJA used for suction are also presented.