Numerical and theoretical investigation of the surface flows of granular materials on heaps

Flows of granular material on ‘non-frozen’ and ‘frozen’ heaps are considered numerically and theoretically in this work. The surface flow on a ‘non-frozen’ heap is first investigated numerically using the discrete element method. The flow profiles of the surface granular flow and the creep motion of particles in the heap are studied. It is shown that the mean velocity of the surface flow exhibits a linear relationship with the distance from the heap surface, while that of the particles in the heap decays exponentially with the distance. The existence of such a creep motion may be attributed to the variation of the porosity distribution of the heap. The granular flow on a ‘frozen’ static heap is also simulated, and compared with the one on the corresponding ‘non-frozen’ heap. The results show that the surface conditions of the heap, to some extent, affect the flow upon it. The surface flow on a static heap is then theoretically examined in detail by using a recently developed continuum model. The depth of the steady-state surface flow and its dependence on wall friction and heap width are investigated. In addition, the theoretical results are compared with the DEM simulation results and the experimental ones in the literature, and qualitatively good agreements are observed.

Graphical abstractFlows of granular material on ‘non-frozen’ and ‘frozen’ heaps are investigated numerically and theoretically. It is shown that the mean velocity of the particles in the ‘non-frozen’ heap decays exponentially with the distance from the heap surface. The surface flow on static heap has a smaller velocity than that on the corresponding ‘non-frozen’ heap. The depth of the steady-state surface flow on the static heap depends on wall friction and heap width. Qualitatively good agreements are observed in the comparisons of the theoretical results with the experimental ones, confirming the applicability of a continuum theory developed recently to the description of the flow profiles of granular surface flow on static heaps.Figure optionsDownload full-size imageDownload as PowerPoint slide