Drag force on a spherical particle moving through a foam: The role of wettability

Experimental measurements are presented of the drag force on a spherical probe particle moving through an aqueous foam at the low speed limit, for particle/bubble radius ratios of 1.5-3.0. In froth flotation, this force is critical for understanding selectivity of these particles. The effect of surface wettability and particle diameter is both explored. A 'hybrid' model of the force is developed and compared with the experimental data. This combines forces due to yield of the foam 'continuum', both in the bulk and at the foam-particle interface, with forces due to attachment/detachment of individual foam nodes from the particle. (C) 2011 Elsevier B.V. All rights reserved.