Eulerian finite element modelling of the cohesive arch in silos

Arching in cohesive granular materials presents significant challenges in industrial bulk solids handling. Here a visco-elastoplastic model of cohesive granular materials is proposed to simulate the arching in flat-bottomed silos using Eulerian finite element method (FEM). Validated against the experimental measurements, the model reasonably predicts the discharge rates and critical outlet widths of the silo under various conditions. The obtained results demonstrate that the critical cohesion coefficient, above which the arching would occur, increases significantly with the filling height of the silo until the filling height is greater than approximately 6.43 times of the outlet width. The static friction coefficient of granular materials also shows a pronounced effect on arching: increasing the static friction from 0.22 to 0.42 leads to an 87% decrease in the critical cohesion coefficient (from 3.85 to below 0.5). By contrast, the upper limit of friction coefficient does not significantly affect the arching. As it increases from 0.4 to 0.9, the critical cohesion coefficient remains constant at 2.15. The pattern of force structure inside granular materials is also discussed based on the numerical model to gain insights into the mechanism of arching.