Simulation of slowly dragging a cylinder through a confined pressurized bed of granular materials using the discrete element method

A nonlinear spring dash pot model to describe the interaction forces between confined granules under high pressures based on Hertz contact theory is proposed. The discrete element method (DEM) is used to simulate the movement and calculate the normal and tangential contact forces among the granules when a cylinder is dragged through a granular bed at low velocities. The time-dependent, total drag force required to pull the circular cylinder is also calculated and used to compare the effect of material and boundary conditions on flow behavior. Simulation results show that drag force increases with cylinder diameter, granular volume fraction, granular size, and the friction coefficient between granules. Drag force was found to be independent of the velocity of the cylinder at low speed, the friction coefficient between the granules and the cylinder, and the friction coefficient between the granules and the container walls.