Simulation of Direct-Current Surface Plasma Discharges in Air for Supersonic Flow Control

A computational model of a plasma discharge for supersonic air flow control is presented. The model is based on a self-consistent, multispecies, continuum description of the plasma with finite-rate chemistry effects. The plasma model is integrated with a compressible Navier-Stokes solver to study the coupled physical effects of the plasma interacting with a M = 3 supersonic flow at freestream pressure of 18 torr and the corresponding effects of the flow on the discharge structure in two dimensions. The species concentrations and gas temperature are examined in the absence and presence of bulk supersonic flow. The peak gas temperature from the computations is found to be 1180 K with the surface plasma alone in the absence of flow and 830 K in the presence of supersonic flow. Different ion species are found to be dominant in the absence and presence of supersonic flow, highlighting the importance of including finite-rate chemistry effects in discharge models for understanding plasma actuator physical phenomena. Electrode polarity effects are investigated, and the cathode upstream actuation is found to be stronger than the actuation strength with the cathode downstream, which is consistent with experimental findings of several groups.