Convergence of equilibrium radial velocity of different particle sizes against grid resolution with runs SI10-4-2-d, SI10-4-2B-d and SI10-4-2C-d. Both the mean drift velocities (circles) and the level of diffusion (vertical bars) agree between the cases of N_x × N_z = 128 × 128, 256 × 256, and 512× 512. This impliesthat our results are not dependent on numerical resolution. Runs SI10-4-2B-d and SI10-4-2C-d were shifted horizontally for better visibility.