The bulk flow behavior of particulate systems is known to be greatly affected by the morphology of the particles from which it is composed. Materials with angular, blocky, or elongated particle shapes will tend to have greater yield strengths and internal friction angles in addition to reduced flow rates through process equipment such as hoppers. While such quantities are readily measured experimentally for a given material, it is difficult to quantitatively assess the specific role of particle shape. In contrast, by using a computational approach such as the discrete element method (DEM), particle characteristics such as shape can be systematically studied and the effect on the bulk system can then be assessed.

In this work, a Schulze ring shear tester is modeled using DEM and the effects of particle shape and particle-particle friction on the bulk friction angles are observed. Monodisperse systems of frictional, non-cohesive particles are modeled with the commercial DEM package EDEM (DEM Solutions Ltd.), and the particle shape is systematically varied from spheres to elongated rods. The bulk friction measurements consisting of the internal friction angle and the wall friction angle are made for each particle shape and a range of input friction coefficients (particle-particle and particle-wall coefficients). For spherical particles, results show that the internal friction angle reaches a plateau for increasing particle-particle friction coefficients. However, if particle rotation is prevented, the internal friction angle increases significantly to large values. Particles of larger aspect ratios also show an increase in the internal friction angle. Movies from the simulations as well as the translational and rotational velocity data give insight into the physics within the system.