  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.
