Numerical simulation of positive streamers interacting with porous dielectric

Porous materials have been employed to regulate the discharge process in several research fields, whereas the complex structure of porous dielectrics impedes the analysis of discharge processes on dielectric surfaces. This paper presents a numerical study of positive streamers in air propagating over a porous dielectric with a random pore structure. We adopt a particle-in-cell model based on Itô diffusion and Kinetic Monte Carlo methods to characterize the electron transport and reactions. The streamer propagation modes, including discharge onset, propagation along the porous dielectric, and the evolution within the pores, are comprehensively investigated. Furthermore, the influence of pore size, applied voltage, and relative permittivity on streamer development is analyzed. The results indicate that the generation and propagation of streamers in the pores are jointly governed by electric field enhancement and surface charging. A representative discharge sequence within the pores includes: early-stage initiation of forward ionization on the pore walls, mid-stage convergence of micro-discharges from different pore regions, and late-stage discharge development along the pore walls.