FRLP - I+D+i - GRUTN - GMG - TRABAJOS DE INVESTIGACIÓN

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    Apparent mass during silo discharge Nonlinear effects related to filling protocols
    (Elsevier, 2017) Peralta, Juan Pablo; Aguirre, María; Geminard, Jean Christophe; Pugnaloni, Luis
    We study the evolution of the force exerted by a granular column on the bottom surface of a silo during its discharge. Previous to the discharge, we prepare the system using different filling procedures: distributed, i.e. a homogeneous rain of grains across the cross-section of the silo; concentric, a granular jet along the silo axis; and a combination of both, i.e. filling half of the silo using one procedure and the second half using the other. We observe that each filling protocol leads to distinctive evolutions of the apparent mass (i.e., the effective weight sensed at the base) during the discharge. Interestingly, the use of combined filling protocols may lead to a reduced apparent mass, smaller than any other achieved with a simple filling. We propose a model based on the Janssen rationale that quantitatively accounts for the latter puzzling experimental observation.
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    Dynamic transition in conveyor belt driven granular flow
    (Elsevier, 2015) Cordero, José; Pugnaloni, Luis
    We consider the flow of disks of diameter d driven by a conveyor belt of dynamic friction coefficient μ through an aperture on a flat barrier. The flow rate presents two distinct regimes. At low belt velocities v the flow rate is proportional to v and to the aperture width A. However, beyond a critical velocity, the flow rate becomes independent of v and proportional to (A − kd)3/2 in correspondence with a two-dimensional Beverloo scaling. In this high-velocity regime we also show that the flow rate is proportional to μ1/2. We discuss that these contrasting behaviors arise from the competition between two characteristic time scales: the typical time a disk takes to stop on the belt after detaching from the granular pack and the time it takes to reach the aperture.