Radial gas velocity (solid line) as a function of r in the simulations adi_Z=0.02_Lr=9au and adi_Z=0.02_Lr=90au. (The dashed lines marks the boundary between the domains of the two simulations.) The velocity is computed as the mass-weighted average over the vertical domain extent and a time-span of 50  and 500 yr, respectively,after an equilibrium dust scale height has been attained in each simulation. The average radial velocity at r ≥ 3 au is plotted as a dotted line and amounts to 0.035 m s⁻¹. This outward motion is caused by the dust drifting radially inwards and its angular momentum being transferred to the gas. However, it is evident that the mean of the velocity is less than its standard deviation, which is equal to 0.16 m s⁻¹. This is a result of the turbulent motions caused by the streaming instability.