Three-dimensional numerical modelling of gas discharges at atmospheric pressure incorporating photoionization phenomena

A three-dimensional (3D) numerical model for the characterization of gas discharges in air at atmospheric pressure incorporating photoionization through the solution of the Helmholtz equation is presented. Initially, comparisons with a two-dimensional (2D) axi-symmetric model are performed in order to assess the validity of the model. Subsequently several discharge instabilities (plasma spots and low pressure inhomogeneities) are considered in order to study their effect on streamer branching and off-axis propagation. Depending on the magnitude and position of the plasma spot, deformations and off-axis propagation of the main discharge channel were obtained. No tendency for branching in small (of the order of 0.1 cm) overvolted discharge gaps was observed.