Research Projects

Granular materials, consisting of discrete solid particles, are ubiquitous in daily activities and industries, as well as natural events like sediment transport and rock avalanches. However, their flow behavior is often unexplored, especially at low shear rates. A recent study revealed that cohesive granular materials exhibit flow inhomogeneities and instabilities, such as shear banding at very low shear rates. This phenomenon is due to the existence of a shear-weakening rheological branch over low shear rates, where the shear stress decreases with increasing shear rate. The more wide the shear-weakening branch is, the more these instabilities are. A previous study suggested that non-spherical granular materials might exhibit a wider shear-weakening branch than their spherical counterpart, leading to increased instances of flow inhomogeneities and instabilities at low shear rates. This project aims to investigate the slow flows of non-spherical grains in detail, develop constitutive rheological relations for the flows of non-spherical granular materials over multi-decade variations of the shear rate, and propose a continuum model to describe potential flow instabilities. The detailed analysis of potential flow instabilities may explain why non-spherical grains are more prone to jamming than spherical ones and suggest better ways to avoid clogging and jamming of non-spherical grains in unsteady, inhomogeneous, slow flow situations as encountered in industries.