Effective Discharge Dynamics for Plasma Actuators

Some effective control parameters for active separation mitigation using asymmetric dielectric barrier discharges is studied by considering the weakly ionized gas flow past a flat plate at angle of attack. A selfconsistent plasma actuator model is employed to couple the electric force field to the momentum of the neutral gas. The equations governing the motion of electrons, ions and neutrals are solved with Poisson equation to study separation control for different parameters. It is observed that dielectric surface becomes negatively charged and a time averaged force acts on the plasma predominantly downstream, with a transverse component towards the wall. Momentum of the plasma couples to neutral gas through collisions, which results enhancement of near-wall momentum yielding a wall-jet-like feature that effectively eliminates the separation bubble. The impact of several physical and geometric parameters such as the amplitude and shape of excitation, dielectric constants, the initial ionization level, and the electrode shape is discussed. It is found that for an optimum distance between the exposed electrodes kept at a single phase the momentum transfer to the neighboring gas is cumulative showing, however, a diminishing return with increasing number of electrodes.