New Macroparticle Coalescing Models That Conserve Particle’s Phase-Space Distribution in 3-D Particle-in-Cell Simulations of Plasmas

Abstract

The number of macroparticles increases dramatically during the particle-in-cell (PIC) simulations of an electron avalanche in high-pressure gas discharges, which always leads to a collapse of simulations. The use of macroparticle coalescing models dynamically decreases the number of macroparticles, but introduces computational errors destructing the conservations of momentum, kinetic energy, and phase-space distribution of the macroparticles. Two new macroparticle coalescing models for 3-D PIC simulations, namely, 2-to-1 and 4-to-2 models, are developed and presented here. Both the models classify macroparticles into eight groups in the velocity space and sort them separately according to the magnitude of the three velocity components. Numerical simulations show that the 4-to-2 model not only conserves the phase-space distribution of the macroparticles but also keeps the deviations of their momentum and kinetic energy at a very low level. The deviations even reduce when the total number of precoalesced macroparticles increases.