Forced silo discharge

M. A. MADRID; J.R. DARIAS; L.A. PUGNALONI

Puerto Varas

Workshop; Southern Workshop on Granular Matter 2018; 2018

The Beverloo scaling for the gravity flow of granular materials through orifices has two distinct universal features: On the one hand, the flow rate is independent of the height of the granular column; on the other hand, the flow rate is fairly insensitive to the material properties of the grains (density, Young?s modulus, friction coefficient, etc.). We show in this work that both universal features are lost if work is done on the system at a high rate. In contrast to viscous fluids, the flow rate increases during discharge if a constant pressure is applied to the free surface of a granular column. Moreover, the flow rate becomes sensitive to the material properties. Nevertheless, the dissipated power scaled by the mean pressure and the flow rate follows a master curve for forced and unforced conditions and for all material properties studied. We show that this new universal feature can be explained if the granular flow in the silo is assumed to be a quasistatic shear flow under the \mu(I)-rheology.