Dense granular flow through a flat-bottomed silo: Comparison of the DEM and continuum models with experiments

The gravity flow of granular materials through a flat-bottomed rectangular silo is examined using experiments, the discrete element method (DEM), and continuum models. The flow is bounded by four flat frictional side walls, and the mass flow rate is controlled by an exit slot. The velocity and wall stresses are measured simultaneously in a steady fully developed zone which occurs far from the upper free surface and the exit slot, and they are compared with predictions of the DEM and the continuum models. The scaled velocities measured adjacent to the front face are in excellent agreement with the DEM. The centreline velocity is predicted to within 5%-30% by the DEM for larger widths. The normal and shear stresses measured at the mid-plane of one of the walls agree to within 5%-20% for the DEM. The DEM results are less sensitive to the spring stiffness k(n), but are more sensitive to the interparticle coefficient of friction mu(p). There are larger discrepancies in the predictions of the continuum models when the effect of the front and rear walls are not included. The approximate inclusion of the latter improves the prediction of the shear stress and the slip velocity.