Modeling Surface Discharge Effects of Atmospheric RF on Gas Flow Control

The advantages of plasma actuators for flow control are being increasingly recognized in the literature in all speed regimes encountered in aerospace applications. Recent experiments with suitably configured atmospheric RF discharges have demonstrated particularly striking effects by reducing or eliminating separation in low-speed flows. In this paper, a finite-element multi-fluid formulation is developed and utilized to model the RF induced plasma dynamics of an asymmetric electrode configuration. Partially ionized helium gas flow is considered over two electrodes, one exposed and one embedded in a thin dielectric material. The exposed electrode is powered with an RF potential and the embedded electrode is considered grounded. In a previous work, the derived electric field for a discharge between two insulated electrodes was coupled to a simple phenomenological model for the transverse velocity in a one-dimensional situation that predicted the anticipated hump in the near wall profile. Here the model is modified for the surface barrier discharge, extended to two-dimensions and applied to a realistic configuration comprised of a flush-mounted surface electrode and a corresponding streamwise displaced electrode embedded in the dielectric. The results extract features of the plasma-wall interaction on the neutral flow field with a self-consistent approach. The computed solutions for the evolution of electric field, space charge distribution and neutral gas densities are presented. The effect of the electric force due to surface discharge on the working gas flow is also demonstrated.