  We use a mesoscopic simulation technique to study the effect of short-ranged
inter-particle attraction on the steady-state sedimentation of colloidal
suspensions. Attractions increase the average sedimentation velocity $v_s$
compared to the pure hard-sphere case, and for strong enough attractions, a
non-monotonic dependence on the packing fraction $\phi$ with a maximum velocity
at intermediate $\phi$ is observed. Attractions also strongly enhance
hydrodynamic velocity fluctuations, which show a pronounced maximum size as a
function of $\phi$. These results are linked to a complex interplay between
hydrodynamics and the formation and break-up of transient many-particle
clusters.
