  We study the local and global rheology of non-Brownian suspensions in a
solvent that is not density-matched, leading to either creaming or
sedimentation of the particles. Both local and global measurements show that
the incomplete density matching leads to the appearance of a critical shear
rate above which the suspension is homogenized by the flow, and below which
sedimentation or creaming happens. We show that the value of the critical shear
rate and its dependence on the experimental parameters are governed by a simple
competition between the viscous and gravitational forces, and present a simple
scaling model that agrees with the experimental results from different types of
experiments (local and global) in different setups and systems.
