Dynamics of non-spherical particles in hopper discharge – Experimental and DEM study

Abstract

Critical knowledge of the discharge of granular materials from a hopper is required to design and handle these materials efficiently in industries. The shape of a particle plays a significant role in the discharge dynamics, with irregular shapes causing more flow rate fluctuations. In this work, a pseudo-2D hopper was used to study the effect of particle shape on particle flow dynamics in the hopper experimentally and computationally. High-speed video camera-based experiments were conducted, and the particle discharge rates and velocity profiles obtained using the Matlab Tool PIVLab were analyzed for non-spherical and spherical particles. Simulations were performed using the in-house GPU-based Discrete Element Modeling (DEM) solvers. The multi-sphere and polyhedral-based DEM methods were adopted to represent the non-spherical shape, with the polyhedral DEM simulations matching closely with the experimental data. The experimental results revealed that the cubes discharged slower than the spheres due to the sharp edges of these particles. The non-spherical nature of these particles also produced flow deformities, such as arching of the particles near the hopper orifice, thereby obstructing the smooth flow. The simulation study was further extended to include three different shapes, and it was observed that with a decrease in particle sphericity, the discharge rate of the particles also decreased. Overall, this study provided analysis of the particle flow inside the hopper by means of mass flowrates, solid fractions, and the radial and axial velocity fields for the spherical and four different-shaped non spherical particles.