Title: 3D Dense Granular Flow Simulation with Discrete Element Method

Author (Talk): Fuping Zhou, ExxonMobil Research and Engineering

Abstract:

Simple shear granular flow under confinement pressure is studied numerically with the 3D Discrete Element Method. Monodisperse spheres are confined in the z- direction between two parallel walls (roughened by a layer of immobilized spheres), with periodic boundary conditions in both the x- and y- directions. The bottom wall is held stationary and the top wall is moved with constant velocity in the x- direction, while maintaining a constant pressure. Beyond a thin boundary layer near the walls, the strain rate becomes independent of position and the medium achieves a uniform macrostate with no spatial gradients. The impact of interstitial fluid is considered by incorporating lubrication forces between the granules when their separations are within a prescribed range. Two distinct states of the flow are observed and separated by a boundary at which percolation of the contact network is lost. In the first state, the contact network spans the system and both the bulk density and the velocity fluctuations decrease while the effective friction coefficient increases with dimensionless shear rate. In the second state, in which the network is broken into finite clusters, the effective friction coefficient is independent of the dimensionless shear rate while the velocity fluctuations increase with it. Finally, two new non-dimensional parameters are proposed which control the state of the granular flow for simple shear and chute flow, both with and without interstitial fluid.