Particle scale height H_p for small particles (size τ_f ≤ 0.002, R ≤ 1.5 mm) over the course of the simulation. The top figure shows the entire simulation, including the sedimentation phase. After 250 orbits, H_p has reached a steady state and the numerical experiment begins. The bottom figure shows only the gas removal phase. Gas is removed exponentially. In the bottom plot, the simulation time is replaced by the solid concentration Z = Σ_solid/ Σ_total. For particles in this size scale, the scale height is determined primarily by Δ, and secondly by Z.