Finite element modelling of wall pressures in a cylindrical silo with conical hopper using an Arbitrary Lagrangian–Eulerian formulation

Abstract

Silos, especially the ones consisting of cylindrical section with conical hopper, are commonly used for bulk material handling in many industries. Whilst the pressure acting on silo walls during filling is reasonably well understood, a reliable prediction of pressure during discharge remains an important open problem for silo design. This paper describes a finite element analysis of the granular flow in a model silo consisting of a cylindrical section with a conical hopper. The computations were performed using an Arbitrary Lagrangian–Eulerian formulation with an explicit time integration approach to permit large deformations and overcome mesh distortion problems. The finite element results of silo pressure were temporally averaged and compared with the experimental observations in a model silo, which shows a satisfactory agreement in the wall pressure distribution. Two critical modelling issues have been addressed in some detail: one is the numerical treatment of the abrupt transition between the cylindrical section and the conical hopper, and the other is the interaction between the granular solid and the silo walls that is modelled using a dynamic friction model in this study. The simulation results show significant pressure fluctuations during silo discharge, which are comparable to the fluctuating pressure patterns reported in previous experiments. Two dominant frequencies are identified from the dynamic pressure, and a scrutinization of the simulation results suggests that the causes may be attributable to the propagation of the longitudinal waves within the stored granular solid and the intermittent macro-slip of the granular solid against the silo wall. These dynamic events could be a source of silo quaking and honking phenomena.