Vibration induced flow in hoppers: continuum and DEM model approaches

A 2D and a 3D discrete element model (DEM) simulation of cohesive spherical particles are applied to assess the benefit of point source vibration to induce flow in wedge-shaped hoppers. The model is closely compared with a continuum model based on arch stability. A significant aspect of this study is the scaling of the continuum system to a discrete system of 500 particles in 2D and 2500 particles in 3D. This illustrates how such models can complement each other. The continuum model can cope with a full-scale industrial system, but is complex with significant assumptions. The discrete approach is relatively simple at the particle level with minimal assumptions but computationally demanding. The DEM model supports the basic conclusions of the continuum model. The vibration source must be located at the appropriate height above the outlet on the hopper to optimise its flow enhancement. Too low and stable arches can form above. Too high and it might not break the stable arches in the material below. The passive/active nature of the material during vibration and flow is also illustrated. The DEM model also shows that low frequency high amplitude vibration can enable flow through small orifices.