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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, 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.

We study the discharge of a two-dimensional silo through small openings via discrete element simulations. We consider the effect of the shape of the grains on the clogging of the flow, focusing on regular polygons and disks. We show that the clogging probability presents a non-linear response as a function of the number of vertexes of the polygons. Also, the clogging probability is strongly dependent on the protocol used to trigger the flow after each clog. We found that the size and shape of the blocking arches display a much larger variability for some polygons, particularly for squares, than for disks.

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