Orientation, Flow, and Clogging in a Two-Dimensional Hopper: Ellipses vs. Disks

TL;DR

This study compares the flow and clogging behavior of ellipses and disks in a 2D hopper, revealing how particle shape and orientation influence flow dynamics and arch formation.

Contribution

It provides new insights into how particle shape and orientation affect hopper flow, clogging, and stress distribution, especially for ellipsoidal particles.

Findings

Ellipse orientation affects clogging probability.

Alignment of ellipses promotes stable arch formation.

Flow characteristics differ between disks and ellipses.

Abstract

Two-dimensional (2D) hopper flow of disks has been extensively studied. Here, we investigate hopper flow of ellipses with aspect ratio $\alpha = 2$, and we contrast that behavior to the flow of disks. We use a quasi-2D hopper containing photoelastic particles to obtain stress/force information. We simultaneously measure the particle motion and stress. We determine several properties, including discharge rates, jamming probabilities, and the number of particles in clogging arches. For both particle types, the size of the opening, $D$, relative to the size of particles, $\ell$ is an important dimensionless measure. The orientation of the ellipses plays an important role in flow rheology and clogging. The alignment of contacting ellipses enhances the probability of forming stable arches. This study offers insight for applications involving the flow of granular materials consisting of ellipsoidal shapes, and possibly other non-spherical shapes.