Hafez, A., Liu, Q., Finkbeiner, T., Alouhali, R. A., Moellendick, T. E & Santamarina, J. C. (2021). The effect of particle shape on discharge and clogging. Scientific Reports, 11 (3309).
Granular flow is common across different fields from energy resource recovery and mineral processing
to grain transport and traffic flow. Migrating particles may jam and form arches that span constrictions
and hinder particle flow. Most studies have investigated the migration and clogging of spherical
particles, however, natural particles are rarely spherical, but exhibit eccentricity, angularity and
roughness. New experiments explore the discharge of cubes, 2D crosses, 3D crosses and spheres
under dry conditions and during particle-laden fluid flow. Variables include orifice-to-particle size ratio
and solidity. Cubes and 3D crosses are the most prone to clogging because of their ability to interlock
or the development of face-to-face contacts that can resist torque and enhance bridging. Spheres
arriving to the orifice must be correctly positioned to create stable bridges, while fat 2D crosses
orient their longest axes in the direction of flowlines across the orifice and favor flow. Intermittent
clogging causes kinetic retardation in particle-laden flow even in the absence of inertial effects; the
gradual increase in the local particle solidity above the constriction enhances particle interactions
and the probability of clogging. The discharge volume before clogging is a Poisson process for small
orifice-to-particle size ratio; however, the clogging probability becomes history-dependent for nonspherical particles at large orifice-to-particle size ratio and high solidities, i.e., when particle–particle
interactions and interlocking gain significance.