The sedimentation of fine particles in liquid foams

Abstract

We investigate the sedimentation of fine particles in liquid channels of foams. The study combines numerical simulations with experiments performed in foams and in isolated vertical foam channels. Results show that particulate motion is controlled by the confinement parameter (λ) and the mobility of the channel surfaces modelled by interfacial shear viscosity. Interestingly, whereas the position of the particle within the channel cross-section is expected to be a relevant parameter, it is shown that in foam there is no effect of this parameter on the sedimentation velocity. For low surface mobities, particles’ velocities are small and almost independent on the size ratio; in opposition, for high surface mobilities, at low λ the particle velocity is always larger than the Stokes velocity, whereas it is always smaller for λ > 0.5. This behaviour has been understood from the generally observed position of moving particles along corners of the channels’ cross-section.