Two-dimensional nonequilibrium fluid models for streamers

The self-consistent, two-dimensional fluid simulation for describing nitrogen gas prebreakdown phenomena under atmospheric pressure is presented in cylindrically symmetric geometry. The models of the electron dynamics are characterized either by an equilibrium single-moment equation or by a nonequilibrium three-moment equation. A more accurate flux-corrected transport (MAFCT) technique, which provides a solution with steep and varying gradients in large dynamic ranges, is used to solve the electron fluid equations. Included in the step-by-step presentation are the electron density, the space-charge electric field, the electron average velocity, the electron mean energy, and the electron power deposition from the initial stage to the later stage when the ionizing channel bridges the gap. The differences between equilibrium and nonequilibrium fluid models are discussed in terms of the formation of ionizing channels and the propagation of streamers