Creeping flow around particles in large yield stress Bingham fluids

Abstract eng:
Yield stress fluids can hold buoyant rigid particles static if their yield stress is large enough. This critical yield number, beyond which there is no flow, is an important parameter to estimate in addressing sedimentation of rigid particles in visco-plastic fluids. As we get close to this limit, viscous dissipation becomes negligible in comparison to the plastic contribution. Employing slipline theory for 2D plastic flows, we are able to approximate the yield number (lower bound) and the shape of the plugs attached to the falling particle in this limit. Numerical experiments of symmetric particles motion in visco-plastic fluid validate the predictions of slipline theory for a wide range of geometries and reveal some astonishing effects.

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