Characterizing flowability of granular materials by onset of jamming in orifice flows

TL;DR

This study investigates the jamming behavior of granular materials in hopper flows, introducing methods to measure flowability and an empirical model to predict jamming onset based on particle properties.

Contribution

It provides experimental methods for measuring jamming onset and an empirical model that accounts for particle shape, size distribution, and friction effects.

Findings

Jamming onset increases with particle elongation and friction.

Good agreement between two independent measurement methods.

Empirical model quantifies effects of particle properties on flowability.

Abstract

This paper describes methods to measure flow rate and jamming onset of granules discharged through a flat-bottom cylindrical hopper with a circular orifice. The intrinsic jamming onset for ideal particles (spherical, monodisperse, smooth) is experimentally measured by two independent methods, with good agreement. For non-ideal particles, the normalized jamming onset increases with elongated granule shape, broadened size distribution and increased friction as measured by the drained angle of repose. An empirical model of the jamming onset is introduced to quantify these effects over the range of materials investigated. The jamming onset can be used as a measure of differentiation between relatively free-flowing granules.