Scale height of the particle layer H_p (top panel) and maximum of the local particle density ρ_p (bottom panel) as a function of time for two 2D models with different numbers of super-particles. Both models have particles of dimensionless stopping time τ_s = 10^-2, a solid abundance of Z = 0.02, a computational domain of 0.2H × 0.2H, and a resolution of 2560H^-1. The blue and green lines represent an average number of particles per cell of and 10, respectively.