A particle-in-cell solution to the silo discharging problem

The problem of flow of a granular material during the process of dischargin g a silo is considered in the present paper. The mechanical behaviour of th e material is described by the use of the model of the elastic-plastic soli d with the Drucker-Prager yield condition and the non-associative flow rule . The phenomenon of friction between the stored material and the silo walls is taken into account-the Coulomb model of friction is used in the analysi s. The problem is analysed by means of the particle-in-cell method-a varian t of the finite element method which enables to solve the pertinent equatio ns of motion on an arbitrary computational mesh and trace state variables a t points of the body chosen independently of the mesh. The method can be re garded as an arbitrary Lagrangian-Eulerian formulation of the finite elemen t method, and overcomes the main drawback of the updated Lagrangian formula tion of FEM related to mesh distortion. The entire process of discharging a silo can be analysed by this approach. The dynamic problem is solved by th e use of the explicit time-integration scheme. Several numerical examples a re included. The plane strain and axisymmetric problems are solved for silo s with flat bottoms and conical hoppers. Some results are compared with exp erimental ones. Copyright (C) 1999 John Wiley & Sons, Ltd.