Abstract
We report two-dimensional simulations of circular and polygonal grains passing through an aperture at the bottom of a silo. The mass flow rate for regular polygons is lower than for disks\red{,} as observed by other authors. We show that both the exit velocity of the grains and the packing fraction are lower for polygons, which leads to the reduced flow rate. We point out the importance of the criteria used to define when two objects of different shape are considered to be of the same size. Depending on this criteria, the mass flow rate may vary significantly for some polygons. Moreover, the particle flow rate is non-trivially related to a combination of mass flow rate, particle shape and particle size. For some polygons, the particle flow rate may be lower or higher than that of the corresponding disks depending on the size comparison criteria. Received: 18 May 2015, Accepted: 30 October 2015; Edited by: F. Melo; Reviewed by: J.-N. Roux, Universite Parsi Est, Laboratoire Navier, Champs-sur-Marne, France; DOI: http://dx.doi.org/10.4279/PIP.070016Cite as: E Goldberg, C M Carlevaro, L A Pugnaloni, Papers in Physics 7, 070016 (2015)This paper, by E Goldberg, C M Carlevaro, L A Pugnaloni, is licensed under the Creative Commons Attribution License 3.0.
Highlights
The flowing properties of granular materials are key in a myriad of industrial processes
We have considered the discharge of circular and polygonal grains from a flat bottomed silo
In agreement with other workers, that for grains of the same mass, the mass flow rate is markedly lower for polygons in comparison with disks
Summary
The flowing properties of granular materials are key in a myriad of industrial processes. Studies on circular grains and on supercircles (rounded squares) in 2D show a significantly lower mass flow rate for the supercircles [11]. These authors compare particles of different shape that have the same long diameter. We will show that this choice has a significant impact on the mass flow rate observed in particles of different shapes. This would complicate our analysis regarding what is the effective size of the particles In this respect, a recent study has shown that an effective size cannot be defined for the flow rate of bidisperse mixtures [20]. The phenomenon is interesting in itself, these instances have been detected and removed from any analysis
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