Clogging of suspensions in bidirectional flow and through obstacle arrays

The flow of granular materials, such as a suspension of macroscopic particles through a network of pores, can lead to clogging relevant to a variety of environmental and industrial flows. We perform experiments using two geometries to investigate dynamics in non-Brownian suspension clogging. In one, we characterize the interaction of grains in a bidirectional suspension flow in which two species travel in opposite directions through a channel and clogging occurs as one species impedes the flow of the other. In the other, transparent PDMS channels are used to transport quasi-2D millifluidic particle suspensions through a network of fixed pillars to characterize the spatial and temporal clogging behavior as obstacle spacing is varied. For bidirectional flow, we measure a sigmoidal clogging probability as a function of total number of grains. Data for varying channel widths collapses indicating clogging occurs at a critical density with stability decreasing with width of the channel. In the millifluidic geometry, we characterize the evolution of clogs and resulting flow in the vicinity of the obstruction via particle tracking. While the number of particles captured increases in time, non-uniform clogging leads to increased fluid velocity, particle streams, and slower accretion.