A mixture of crushing and segregation: The complexity of grainsize in natural granular flows

Marks, Benjy; Einav, Itai

doi:10.1002/2014gl062470

Cited by 36 publications

(16 citation statements)

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“…Brittleness adds complexity to the dynamics of granular flows 19 and can alter the propagation of density fronts often observed during the flow of loose, non-brittle granular media [20][21][22] . Finally, we recall another form of strain localization that occurs during the extension of metallic alloys-known as the Portevin-Le Châtelier (PLC) effect [23][24][25] .…”

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Dynamic patterns of compaction in brittle porous media

et al. 2015

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Here, using a new heuristic lattice spring model undergoing repeated crushing events, we first predict the possible emergence of new types of dynamic compaction; we then discover and confirm these new patterns experimentally in compressed cereal packs. In total, we distinguish three observed compaction patterns: short-lived erratic compaction bands, multiple oscillatory propagating compaction bands reminiscent of critical phenomena near phase transitions, and di used irreversible densification. The manifestation of these three di erent patterns is mapped in a phase diagram using two dimensionless groups that represent fabric collapse and external dissipation.Compaction of brittle porous media is of central importance in industry and science, and has many ramifications, from destruction waves during meteoritic impacts 7 to the formation of density heterogeneities in pharmaceutical pills 8 and permeability barriers in rocks 9,10 . Previous work on brittle porous media has generally revealed two forms of compaction patterns: stationary and oscillatory propagating compaction bands. Specifically, stationary compaction bands with localized intense volumetric strain rate have been frequently observed in a wide range of brittle porous materials, including rocks 1-3 , foams 4 and honeycomb materials 11 . The formation of such bands has been rationalized mathematically using continuum models of viscoplasticity 12,13 or breakage mechanics 14,15 , with the latter connecting the process directly to the physics of grain breakage and pore collapse.The formation of oscillatory propagating compaction bands in porous media was discovered more recently by Valdes et al.5 , via uniaxially confined compression experiments on puffed rice packs (Fig. 1a). Similar to stationary compaction bands, the material within these bands experienced high volumetric strain rates accommodated by severe grain breakage and pore collapse. By comparing experiments on material placed in containers with different boundary roughness, this work motivated a connection between compaction dynamics to how energy is dissipated outside.More recently, similar experiments on dry foamy snow 6 also revealed oscillatory propagating compaction bands, although with only one or two oscillations per test (this will be discussed later, in Fig. 2g-i). This form of compaction was captured using a phenomenological continuum model for snow, with an assumed elastoplastic yield function, power-law density dependence, shearinduced bond failure, strength recovery due to sintering, and nonlocality of damage 6 . The need for these assumptions indicates that the underlying mechanisms that control the emergence of oscillatory compaction bands are not clear yet.In this paper we present experiments that unfold novel compaction patterns in brittle porous media. We show that all the observed patterns can be explained using a simple lattice spring model. We then map the manifested patterns in terms of a phase diagram that covers system and material parameters, applicable for brittle porous...

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Dynamic patterns of compaction in brittle porous media

et al. 2015

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“…Polydisperse segregation is more difficult to handle analytically. Only a handful of studies have proposed models for polydisperse granular segregation, and these have been limited to the idealized case of streamwise‐periodic chute flow in which periodic streamwise boundary conditions are used to model fully developed segregation in a section of a chute …”

Section: Introductionmentioning

confidence: 99%

“…For example, Marks et al developed a continuum model for polydisperse segregation in a periodic chute that relies on a fitting parameter determined from DEM simulations. Recently, the same group used a stochastic lattice model incorporating the effects of segregation, mixing, and crushing to predict steady‐state particle size distributions in uniformly sheared granular flows in a periodic chute . Although this approach connects microscale and macroscale advection‐driven processes for polydisperse systems, its agreement with experimentally measured particle‐size distributions is only qualitative.…”

Section: Introductionmentioning

confidence: 99%

“…This makes it difficult to extend the results to specific particle sizes, shapes, and densities or to generalize the model to a continuous distribution of particle sizes or to other flow geometries. Furthermore, previous models of polydisperse segregation have focused on fully developed segregation in a streamwise‐periodic chute using DEM simulations. Although the streamwise‐periodic chute geometry is suitable for initial testing and validation of segregation models due to its simplicity, this geometry only produces segregation in the depthwise direction and corresponds to a prefilled chute infinite in length or to the downstream region of the chute where material advected from the top of the chute has not reached.…”

Section: Introductionmentioning

confidence: 99%

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Modeling segregation of polydisperse granular materials in developing and transient free‐surface flows

et al. 2019

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Predicting segregation and mixing of polydisperse granular materials in industrial processes remains a challenging problem. Here, we extend the application of a general predictive continuum model that captures the effects of segregation, diffusion, and advection in two ways. First, we consider polydisperse segregating flow in developing steady segregation and in developing unsteady segregation. In both cases, several terms in the model that were zero in the previously examined case of fully developed streamwise‐periodic steady segregation in a chute are now non‐zero, which makes application of the model substantially more challenging. Second, we apply the polydisperse approach to density polydisperse materials with the same particle size. Predictions of the model agree quantitatively with experimentally validated discrete element method (DEM) simulations of both size polydisperse and density polydisperse mixtures having uniform, triangular, and log‐normal distributions. © 2018 American Institute of Chemical Engineers AIChE J, 65: 882–893, 2019

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“…Such grain crushing effect has been studied extensively in terms of resulting grain size distribution [31,33], of single grain crushing mechanics [22,34,36], of quasi-static one-dimensional compression [23,26] and shear [5,19] and of their constitutive modeling [8,14,28]. However, to authors' knowledge, such constitutive models are constructed mostly within the framework of quasi-static deformation.…”

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Constitutive Modeling of Granular Geo-Materials Under High-Speed Impact

Matsushima

Sato

2017

Springer Series in Geomechanics and Geoengineering

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A constitutive model of crushable granular geomaterials subjected to high pressure/high speed compression is proposed in this study. The proposed model is based on a micromechanical elasticity model of mono-disperse granular materials [2], and it is extended into well-graded ones in a simple manner. A geometrical recursive equation is introduced to describe the confined crushing process of granular materials. High-pressure Equation of States of solid [21] is also incorporated into the model. The basic response of the proposed model is compared with some experimental data.

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A mixture of crushing and segregation: The complexity of grainsize in natural granular flows

Cited by 36 publications

References 35 publications

Dynamic patterns of compaction in brittle porous media

Dynamic patterns of compaction in brittle porous media

Modeling segregation of polydisperse granular materials in developing and transient free‐surface flows

Constitutive Modeling of Granular Geo-Materials Under High-Speed Impact

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