Three-dimensional numerical simulation of branching structure in surface dielectric-barrier-discharge

Surface dielectric-barrier-discharge (DBD) has been studied to improve the insulating performance of electric devices. In some experiments, spanwise non-uniform branching structures of the streamer have been observed. In this study, we conducted three-dimensional numerical simulation of the surface DBD with a small protrusion of exposed electrode using a plasma fluid model. The branching structures are successfully obtained when a step-like positive voltage is applied, and the surface charge distribution of the streamer is similar to the experimental result. Simulations considering various size of the protrusion and sub-atmospheric pressure conditions are conducted to investigate three-dimensional discharge structure of the surface DBD. The size of protrusion affects the width in the spanwise direction of the branching structure that is formed from the electrode edge. The branched streamers propagate over a long distance in spanwise direction for the case of the larger protrusion. Under sub-atmospheric pressure conditions, the width in the spanwise distribution of the branching structure becomes wider than that for the atmospheric pressure conditions. Elaborate comparisons of branching structures under each condition and important factors that affect the branching structure such as grid convergence will be discussed in the full paper.