Numerical investigation on the clogging-collapsing events in granular discharge

Abstract

Granular flow in hoppers is widely encountered in industries and daily life. Despite its ubiquity, understanding on its basic flow behavior is still limited. Typically, the flow may be interrupted by the formation of arches and the phase transition ensues, and in general these arches may not collapse without external energy input such as vibration. However, in this study, the rare events of granular flow arrested by the formation of unstable arches and then restarted by their spontaneous collapsing, or the clogging-collapsing events, were observed in both lab experiments and numerical simulations in the discrete element method (DEM). It was demonstrated that the clogging may result from the coordinated evolution of the entire force chain system and the kinetic energy dissipated incompletely in bulk is mainly responsible for the collapsing. The evolution of the kinetic energy displays different modes in the clogging-collapsing and permanent clogging events, suggesting that the collapsing can be predicted by monitoring the variance of the kinetic energy. • Experimental and numerical study on the clogging-collapsing events in hoppers. • Imperfect arches with concave links found in temporal clogging. • Temporal arches bearing light load and supported by tangential contact forces. • Kinetic energy fluctuating at fine amplitude during temporal clogging. • Kinetic energy level and its fluctuation may indicate instable packing.