Granular particle-shape heterogeneous mixtures discharging through a silo

AVK Reddy and S Kumar and KA Reddy, JOURNAL OF FLUID MECHANICS, 912, A22 (2021).

DOI: 10.1017/jfm.2020.1071

Process industries often involve handling non-cohesive solid materials which vary in size and shape. A comprehensive understanding of such systems helps in effective handling of industrial operations. Here, we studied heterogeneous mixtures of dumbbells and discs flowing out of a two-dimensional silo using discrete element method simulations. We analysed discharge dynamics of the mixtures in two regimes, namely the free-flow regime (W/d >= 15) and the interrupted flow regime (W/d <= 10), where W and d are the orifice width and diameter of each of the circles of a dumbbell. One of the intriguing results is a decrease in the flow rate Q of mixtures with an increase in the fraction of dumbbells X-db in both of the regimes analysed. This can be attributed to the geometrical interlocking among the particles and a hindrance to the rotation of dumbbells. The time-averaged (coarse-grained) flow fields reveal an increase in the size of the stagnant zone beside the orifice with an increase in X-db. The stagnant zone hinders the particles flowing next to it, which is another reason for a decrease in Q with an increase in X-db. In the interrupted flow regime, we investigated clogged states of the mixtures using arch morphology, the fraction of dumbbells and number of particles in an arch, and avalanche sizes.

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