The frictional flow of a dense granular material based on the dilatant double shearing model

Slow flow of granular materials, which typically occurs during the emptying of industrial storage hoppers and bins, has great industrial relevance. In the present study, we have employed our newly developed dilatant double shearing model [H. Zhu, M.M. Mehrabadi, M. Massoudi, Incorporating the effects of fabric in the dilatant double shearing model for granular materials, Int. J. Plast. 22 (2006) 628-653] to study the slow flow of a frictional, dense granular material. Although most models pertain only to the fully developed granular flow, the application of the dilatant double shearing model is shown to be valid from the onset of granular flow to the fully developed granular flow. In this paper, we use the finite element program ABAQUS/Explicit to numerically simulate the granular Couette flow and the frictional granular flow in a silo. For the granular Couette flow, the relative density variation and the velocity profile obtained by using the dilatant double shearing model are in good quantitative agreement with those obtained from a DEM simulation. For the frictional flow in a silo, the major principal stress directions are obtained at various time steps after the onset of silo discharge. We find that, in the hopper zone, the arching of the granular material between the sloping hopper walls is clearly demonstrated by the change in direction of the major principal stress. We also compare the pressure distribution along the wall before and after the onset of silo discharge. The numerical results show that the dilatant double shearing model is capable of capturing the essential features of the frictional granular flow.