Clogging transition of granular flow in porous structures

The clogging transition of granular flow through a disordered porous structure is investigated by threedimensional discrete element simulations. Results reveal the existence of an intermittent flow state, which has been already observed for active particles or agitated grains, but is absent in single-pore flows of passive particles. Interestingly, the analysis of the intermittent dynamics shows similar attributes to the bottleneck flow of active grains, i.e., exponential distribution of flowing intervals and power-law tails for the clogging times. Precisely, based on the exponent of the power-law tail, a clogging phase diagram for porous structures is proposed in the plane of the scaled pore size D/dp and the friction coefficient mu s. Then, we demonstrate that the intermittency arises from a delay in the dissipation of particles' kinetic energy after clogging imposed by the porous structure. Finally, the maximum achievable particle flow rate driven by gravity is predicted from the Froude number Frm, which linearly scales with the pore size and the friction coefficient.