The three components of the particle velocity as a function of the radial position within a grid cell. Three grid cells were chosen at t = 45T_orb of the run SI128_e0.3, one with the highest particle density in the box, one with a particle density close to 100 times the gas density and finally one with a particle density close to 10 times the gas density. Both systematic and random particle motion is present within the grid cells. The Keplerian shear is clearly visible in the y-velocity (marked with a solid line in the middle panel). The cells with the highest density have generally a slower random motion and are thus more affected by the Keplerian shear.