Jamming, Self-Filtration and Cake Growth in Concentrated Particle Suspensions

We study the flows of concentrated particle suspensions driven through a circular orifice. Above a critical concentration, a jammed structure (i.e., quasi-solid sphere) often forms in the flow and at the entrance of the geometrical constriction. Once occurred this jammed structure grows fast as time t passes and produces a reduction in the solid concentration downstream. Our analysis shows that a combination of the particle jamming, the self-filtration, and the cake-formation with the flow passing through the pores of the jammed solid is responsible for the occurrence of such phenomena. Based on this mechanism, we establish a mathematical model to show how the jammed structure is propagated. Our results suggest that the size D of the jammed structure in this case is proportional to a 1/3 power of the time t. Experiments also support this conclusion.