FE-simulations of rapid silo flow with a polar elasto-plastic constitutive model

The paper presents results on numerical modelling of rapid flow of granular materials in a model silo with convergent smooth walls. The calculations were performed with a finite element method based on a polar elasto-plastic constitutive relation by Muhlhaus (1995). The relation differs from the conventional theory of plasticity by the presence of Cosserat rotations and couple stresses using a mean grain diameter as a characteristic length. The characteristic length causes that numerical results do not depend upon the mesh discretisation. The model tests on rapid silo flow of glass beads performed by Renner in a glass hopper with a large wall inclination from the bottom were numerically simulated. The plane strain FE-calculations were performed by taking into account inertial forces and linear viscous damping. A satisfactory agreement between numerical and experimental results was obtained. Advantages and limitations of a continuum approach for simulations of rapid silo flow were outlined.