Mach number as a functionof r and z in two simulations with dust and an isothermal gas equation of state. As in the dust-free equivalent (compare with Fig. 1), the vertical shear instability induces large-scale perturbations away from the midplane. In the simulation iso_Z=0.02_Lr=90au_Lz=4Hg (left panel), in which we initialize the dust at the beginning, small-scale perturbations can be seen at all radii in the midplane. These perturbations are also observable in the simulation iso_Z=0.02_Lr=90au_Lz=4Hg_tdinit=50kyr (right panel), in which the dust is introduced after 50 kyr, although not at all radii and extending to greater heights. The inlays with a vertical extent of 0.6 gas scale heights show the enlarged perturbations. However, such small-scale perturbations do not exist in the corresponding simulation without dust.