Simulations of a heavy ball falling through a sheared suspension

Abstract eng:
In recent experiments, Blanc, Lemaire and Peters dropped a heavy sphere through a concentrated suspension of smaller, neutrally buoyant particles. They found that the application of a lateral oscillatory shear flow caused the heavy ball to fall faster on average; and that for highly concentrated suspensions, at certain moments of the cycle of shear oscillation, the heavy ball moves upwards. We use Accelerated Stokesian Dynamics to model these experiments and other related scenarios. We show how the motion of the heavy particle depends on two key dimensionless parameters: the frequency of the oscillations (relative to a typical settling time) and the strength of repulsive interparticle forces, such as DLVO, relative to the buoyancy-adjusted weight of the heavy ball. At the conference, we will also present results on the dependence on oscillation amplitude, suspension concentration, and the orientation of the shear flow.

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