Granular packing: numerical simulation and the characterisation of the effect of particle shape

Guises, Romain; Xiang, Jiansheng; Latham, John; Munjiza, Ante

doi:10.1007/s10035-009-0148-0

Cited by 96 publications

(47 citation statements)

References 21 publications

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“…In contrast, we find packings of frictional ellipsoids to be hyperstatic over the whole range of ϕ g studied, in agreement with numerical simulation including friction [26,27].…”

supporting

confidence: 67%

Local Origin of Global Contact Numbers in Frictional Ellipsoid Packings

et al. 2015

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In particulate soft matter systems the average number of contacts Z of a particle is an important predictor of the mechanical properties of the system. Using x-ray tomography, we analyze packings of frictional, oblate ellipsoids of various aspect ratios α, prepared at different global volume fractions ϕ g . We find that Z is a monotonically increasing function of ϕ g for all α. We demonstrate that this functional dependence can be explained by a local analysis where each particle is described by its local volume fraction ϕ l computed from a Voronoi tessellation. Z can be expressed as an integral over all values of ϕ l :The local contact number function Z l ðϕ l ; α; XÞ describes the relevant physics in term of locally defined variables only, including possible higher order terms X. The conditional probability Pðϕ l jϕ g Þ to find a specific value of ϕ l given a global packing fraction ϕ g is found to be independent of α and X. Our results demonstrate that for frictional particles a local approach is not only a theoretical requirement but also feasible. The average number of contacts Z that a particle forms with its neighbors is the basic control parameter in the theory of particulate systems known as the jamming paradigm [1,2], where Z is a function of the difference between the global volume fraction ϕ g and some critical value ϕ J . For soft, frictionless spheres (a practical example would be an emulsion) this is indeed a good description [3] because additional contacts are formed by the globally isotropic compression of the particles which also increases ϕ g . However, in frictional granular media such as sand, salt, or sugar the control of ϕ g is not achieved by compression but by changing the geometric structure of the sample; if we want to fill more grains into a storage container we do not compress them with a piston, but we tap the container a couple of times on the counter top.But if Z and ϕ g are not simultaneously controlled by a globally defined parameter such as pressure, the idea of a function Zðϕ g Þ runs into an epistemological problem: contacts are formed at the scale of individual particles and their neighbors. At this scale the global ϕ g is not only undefined, it would even be impossible for a particle scale demon to compute ϕ g by averaging over the volume of the neighboring particles. The spatial correlations between Voronoi volumes [4-6] would require it to gather information from a significantly larger volume than the direct neighbors.To date, only two theoretical approaches have studied Z from a local perspective: Song et al. [7] used a mean-field ansatz to derive a functional dependence between Z and the Voronoi volume of a sphere. This ansatz has recently been expanded to arbitrary shapes composed of the unions and intersections of frictionless spheres [8,9]. Second, Clusel et al. [10,11] developed the granocentric model which predicts the probability distribution of contacts in jammed, polydisperse emulsions. The applicability of the granocentric model to frictional discs has been sho...

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“…In contrast, we find packings of frictional ellipsoids to be hyperstatic over the whole range of ϕ g studied, in agreement with numerical simulation including friction [26,27].…”

supporting

confidence: 67%

Local Origin of Global Contact Numbers in Frictional Ellipsoid Packings

et al. 2015

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“…11), indicating that the shape of the filler particles affects the bending stiffness of a Vacu-SL shaft and that edgy particles provide higher bending stiffness than rounded ones. This agrees with literature as discussed above [19][20][21][22][23].…”

Section: Shapesupporting

confidence: 81%

“…Olson et al performed experiments on avalanches in piles of particles [19]. They showed that the stability of a pile Other researches showed that particle shape is an important factor in packing stability [20][21][22][23] and that spheres and ellipsoids have similar rolling abilities [24]. Vacu-SL shafts filled with edgy particles are therefore expected to have a higher bending stiffness than those filled with spheres or ellipsoids.…”

Section: Theory and Literaturementioning

confidence: 99%

Vacuum packed particles as flexible endoscope guides with controllable rigidity

et al. 2010

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In order to fully benefit from the functionalities of flexible endoscopes in surgery a simple shaft-guide that can be used to support the flexible endoscope shaft is required. Such a shaft-guide must be flexible during insertion into the human body and rigidified when properly positioned to support the flexible endoscope shaft. A shaft-guide called 'Vacu-SL' was designed, consisting of a foil tube, filled with particles, that is rigidified by creating a vacuum in its tube. It is expected that the bending stiffness of a loaded, rigidified Vacu-SL shaft-guide is significantly influenced by the shape, hardness and size of the filler particles used. The goal of this study was to find the relations between the filler particles' size, shape and hardness and a rigidified Vacu-SL shaft-guide's bending stiffness. Vacu-SL test models were made using polystyrene, acrylic glass, glass, steel, and corundum particles as spheres, pebbles and granulate, with average diameters between 0.16-1.7 mm. These test models were rigidified and then loaded in a tensile tester. The forces needed for 5 and 10 mm deflections of the rigidified test models were measured. The results show that particle size, shape and hardness all influence a rigidified Vacu-SL shaft-guide's bending stiffness. Size and hardness showed an optimum and granules performed better than spheres. Although the maximally measured bending stiffness might be insufficient to enable proper guidance of flexible endoscope shafts, the results suggest several ways to successfully improve the Vacu-SL shaft-guide.

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“…These include the effect of particle shape on packing fraction [11,12], wall pressures in a silo discharge [13], coordination number [14], jamming [15], and stress propagation in granular piles [16]. Despite these efforts, the aspect ratio has only very recently been systematically modified to analyze the special features that particle shape asymmetry may introduce in the packing [11], [17]- [19]. Moreover, there is currently increasing interest in the effect that faceted particles have on the global behavior of granular materials [20,21].…”

Section: Introductionmentioning

confidence: 99%

Granular packings of elongated faceted particles deposited under gravity

Hidalgo¹,

Zuriguel²,

Maza³

et al. 2010

J. Stat. Mech.

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Abstract. We report experimental and theoretical results of the effect that particle shape has on the packing properties of granular materials. We have systematically measured the particle angular distribution, the cluster size distribution and the stress profiles of ensembles of faceted elongated particles deposited in a bidimensional box. Stress transmission through this granular system has been numerically simulated using a two-dimensional model of irregular particles. For grains of maximum symmetry (squares), the stress propagation localizes and forms chain-like forces analogous to those observed for granular materials composed of spheres. For thick layers of grains, a pressure saturation is observed for deposit depths beyond a characteristic length. This scenario correlates with packing morphology and can be understood in terms of stochastic models of aggregation and random multiplicative processes. As grains elongate and lose their symmetry, stress propagation is strongly affected. Lateral force transmission becomes less favored than vertical transfer, and hence, an increase in the pressure develops with depth, hindering force saturation.

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Granular packing: numerical simulation and the characterisation of the effect of particle shape

Cited by 96 publications

References 21 publications

Local Origin of Global Contact Numbers in Frictional Ellipsoid Packings

Local Origin of Global Contact Numbers in Frictional Ellipsoid Packings

Vacuum packed particles as flexible endoscope guides with controllable rigidity

Granular packings of elongated faceted particles deposited under gravity

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