Theoretical and Experimental Investigation of Bidisperse Particle-Laden Flows on an Incline

Abstract

We investigate constant flux bidensity slurries and constant volume bidisperse slurries on an incline. The former mixture consists of two negatively buoyant particle species with the same diameter and different densities, while the latter slurry consists of a single negatively buoyant species of particle but with two distinct diameters. For all experiments, an interplay between two key forces, shear induced migration and gravitational settling, result in the formation of two distinct regimes, ridged and settled, and a third transient regime, well mixed. We develop theoretical models and simulations to compare against our experimental results, as well as produce a phase diagram for constant flux bidensity that can predict the long term regimes of slurries. Additionally, we observe an unexpected settling phenomenon in the bidisperse experiments where long term particle front order is the opposite of what we expect. At first, the large particles settle out of the flow, however we observe that with enough time, the larger particle front migrates in front of the smaller particle front, indicating that the larger particles do not completely sink.

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