Maximization of granular outflow by oblique exits and by obstacles

Zelinski, Björn; Goles, Éric; Markus, Mario

doi:10.1063/1.3103329

Cited by 8 publications

(3 citation statements)

References 13 publications

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“…For a three dimensional hopper there exists a critical orifice width above which the system never jams [4] while no such limit exists for a two dimensional system which can jam for large enough orifice widths [5]. It has been shown that the output flow rate from a hopper can be increased as large as 10% by placing suitable inserts within at appropriate locations [6][7][8]. This also decreases the probability of jamming by about two orders of magnitude [9].…”

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confidence: 99%

Spontaneous jamming and unjamming in a hopper with multiple exit orifices

2014

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We show that the flow of granular material inside a two-dimensional flat bottomed hopper is altered significantly by having more than one exit orifice. For hoppers with small orifice widths, intermittent flow through one orifice enables the resumption of flow through the adjacent jammed orifice, thus displaying a sequence of jamming and unjamming events. Using discrete element simulations, we show that the total amount of granular material (i.e., avalanche size) emanating from all the orifices combined can be enhanced by about an order of magnitude difference by simply adjusting the interorifice distance. The unjamming is driven primarily by fluctuations alone when the interorifice distance is large, but when the orifices are brought close enough, the fluctuations along with the mean flow cause the flow to unjam.

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confidence: 99%

Spontaneous jamming and unjamming in a hopper with multiple exit orifices

2014

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“…Instead, the placement of obstacles is usually aimed to improve the flow and to the reduction of undesirable wall stresses. Indeed, most of the studies about silos and obstacles are performed with such a large outlet size that clogging is practically impossible [14][15][16][17].…”

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confidence: 99%

Flow and clogging in a silo with an obstacle above the orifice

et al. 2012

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In a recent paper [Zuriguel et al., Phys. Rev. Lett. 107, 278001 (2011)] it has been shown that the presence of an obstacle above the outlet can significatively reduce the clogging probability of granular matter pouring from a silo. The amount of this reduction strongly depends on the obstacle position. In this work, we present new measurements to analyze different outlet sizes, extending foregoing results and revealing that the effect of the obstacle is enhanced as the outlet size is increased. In addition, the effect of the obstacle position on the flow rate properties and in the geometrical features of arches is studied. These results reinforce previous evidence of the pressure reduction induced by the obstacle. In addition, it is shown how the mean avalanche size and the average flow rate are not necessarily linked. On the other hand, a close relationship is suggested between the mean avalanche size and the flow rate fluctuations.

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“…A practical solution that is commonly implemented to improve the flow in both scenarios, people escaping from a room and the discharge of a silo, is the placement of an obstacle (or insert) just before (or above) the exit [2,[12][13][14][15][16][17][18]. In the case of the silo discharge, selecting the right insert position and size has been proved to increase the flow rate up to 10% [17,18].…”

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Silo Clogging Reduction by the Presence of an Obstacle

et al. 2011

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We present experimental results on the effect that inserting an obstacle just above the outlet of a silo has on the clogging process. We find that, if the obstacle position is properly selected, the probability that the granular flow is arrested can be reduced by a factor of 100. This dramatic effect occurs without any remarkable modification of the flow rate or the packing fraction above the outlet, which are discarded as the cause of the change in the clogging probability. Hence, inspired by previous results of pedestrian crowd dynamics, we propose that the physical mechanism behind the clogging reduction is a pressure decrease in the region of arch formation.

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Maximization of granular outflow by oblique exits and by obstacles

Cited by 8 publications

References 13 publications

Spontaneous jamming and unjamming in a hopper with multiple exit orifices

Spontaneous jamming and unjamming in a hopper with multiple exit orifices

Flow and clogging in a silo with an obstacle above the orifice

Silo Clogging Reduction by the Presence of an Obstacle

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