An experimental investigation of the intrinsic convection in a sedimenting suspension

The sedimentation of spheres in a Newtonian fluid is experimentally studied under creeping flow conditions. The mean particle settling velocity and the particle velocity fluctuations are measured across the width of the sedimentation cell. We show that there can be a global intrinsic convection of the suspension superimposed on the settling motion of the particles. Unlike the predictions of the dilute theories of intrinsic convection, this effect is found to be small and even to disappear with increasing concentrations. We also find that there is an ordering of the suspension near the wall, which may be responsible for the observed small magnitude of the convection.

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