Extrusion of dense suspensions: particle dynamics and self-filtering

Understanding the extrusion of particulate suspensions is important for manufacturing applications as the composition of the prepared material can be significantly affected by the process. In this study, we experimentally investigate the flow of a dense suspension of non-Brownian particles through a quasi-bidimensional channel under flow rate-driven conditions. We also systematically vary the angle of the constriction, studying both slightly tapered and hopper-like channels. We analyze the discharge rate of solid material and fluid by measuring the number of particles crossing a constriction per unit time, evaluating the local volume fraction, and examining the particle velocity profile at the outlet. Our experiments show that while the discharged solid fraction can be well-predicted at sufficiently large constriction widths, self-filtration is observed when decreasing the width of the constriction. The results are compared to the discharge of a silo, and a common framework is developed to predict the evolution of the flow rate of particles when varying the geometry of the system.