Numerical Study of Gas-Dynamic and Thermal Processes in a Pulsed Electric Discharge

The processes accompanying the formation of a contracted (columnar) high-current nanosecond electric discharge in subcentimeter gaps filled with nitrogen are numerically investigated in this work. The space between two flat electrodes is considered in the case when a potential difference of 25 kV is instantly established between them. The voltage is applied for a time interval of 200 ns and then instantly removed. The characteristics of the nonthermal and thermal stages of electric-discharge development are studied, namely: the formation and growth of a streamer, the closure of a discharge gap by a streamer, the formation of a plasma channel, secondary ionization waves, and an increase in current density and temperature in the axial region of the channel. After switching off the electric field, the gas-dynamic processes associated with the discharge thermal effect on a neutral gas are investigated. Gas-dynamic processes are determined by the propagation of shock waves and rarefaction waves in the radial direction with respect to the axis of symmetry. The quantitative values of both the electric field (electron density and intensity) and gas-dynamic parameters (temperature, pressure, and gas velocity) are determined.