Modeling Granular Segregation during Hopper Dischargevia Discrete Element Methods

摘要

Granular materials containing particles of various sizes, shapes, and densities are presentacross a wide variety of industries including those handling pharmaceuticals, food and agriculturalproducts, and chemicals. Differences in these particle properties may lead to segregation of thematerial upon transport or other handling. The flow of granular material within a hopper is onesuch process that may induce segregation. This segregation is problematic in that product quality isusually dependent on maintaining homogeneity of the blend.The present work aims to investigate the causes and extent of segregation of granularmaterials during discharge from a hopper using the discrete element method (DEM). The granularmaterial is modeled as bidisperse, frictional, inelastic spheres, and interstitial fluid effects areneglected. A soft-particle contact model is implemented using the hysteretic spring model ofWalton and Braun [J. Rheol. 30 (1986) 949-980] to model the normal forces, and Coulombicfriction to model the tangential forces.This work investigates hopper flow segregation as a function of particle properties such asdiameter ratio, mass fraction of fines, and coefficients of friction, as well as hopper geometries suchas hopper wall angle and fill height. Preliminary results indicate that the extent of segregationincreases with increasing particle diameter ratio and/or decreasing mass fraction of the smallspecies. Additionally, segregation becomes more prevalent as the hopper wall angle increases withrespect to the vertical.