Particle density ρ_p as a function of solid concentration (left) and height (right). The solid concentration is Z = Σ_solid/ Σ_total. The left figure shows ρ_p at the midplane (height z = 0) as a function of Z. The right figure shows ρ_p at Z = 0.08 as a function of the z coordinate. The particle density is measured in terms of the initial gas density ρ₀. All the simulations have particle size τ_f = 0.002. Two runs have a standard pressure support (Δ = 0.05) and two have a reduced pressure support (Δ = 0.025). Two runs have 128 × 128 grid resolution and two are 256 × 256. There is no evidence of the density cusp predicted by Sekiya (1998) and Youdin & Shu (2002). The Δ = 0.05 and Δ = 0.025 runs should have clear cusps after Z ~ 0.10 and Z ~ 0.02 respectively (Youdin & Shu 2002). These simulations may have an additional source of mixing that inhibits the formation of the Sekiya-Youdin-Shu cusp. The result is the same for smaller, τ_f = 0.001 particles (not shown).