Collective effects in the sedimentation of particles in a viscoelastic fluid

Abstract

The sedimentation of a suspension of rigid spherical particles in a polymeric fluid is studied with experiments and numerical simulations. It is shown that settling in a viscoelastic Boger fluid is time-dependent and inhomogeneous; both experiments and simulations exhibit the formation of particle-rich, fast-settling regions and particle-depleted regions with back flow (shown). When a cross shear flow is imposed, the mean particle settling rate is drastically reduced, suggesting that both fluid elasticity and the particle volume fraction of the suspension have important effects.