Granular segregation in dense systems: the role of statistical mechanics and entropy

Schröter, Matthias; Daniels, Karen E.

doi:10.48550/arxiv.1206.4101

Cited by 2 publications

(2 citation statements)

References 57 publications

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“…Because the exact mechanism of segregation is still a subject of debate [18,21,33], there is no universally agreed upon continuum theory. Nonetheless, one-dimensional (1D) continuum models generally describe the vertical evolution of concentrations of binary mixtures through time with a phenomenological advection-diffusion equation [16,20].…”

Section: Advection-diffusion Segregation Modelmentioning

confidence: 99%

River-bed armouring as a granular segregation phenomenon

et al. 2017

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River bed-load transport is a kind of dense granular flow, and such flows are known to segregate grains. While gravel-river beds typically have an “armoured” layer of coarse grains on the surface, which acts to protect finer particles underneath from erosion, the contribution of granular physics to river-bed armouring has not yet been investigated. Here we examine these connections in a laboratory river with bimodal sediment size, by tracking the motion of particles from the surface to deep inside the bed, and find that armour develops by two distinct mechanisms. Bed-load transport in the near-surface layer drives rapid, shear rate-dependent advective segregation. Creeping grains beneath the bed-load layer give rise to slow but persistent diffusion-dominated segregation. We verify these findings with a continuum phenomenological model and discrete element method simulations. Our experiments suggest that some river-bed armouring may be due to granular segregation from below—rather than fluid-driven sorting from above—while also providing new insights on the mechanics of segregation that are relevant to a wide range of granular flows.

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Section: Advection-diffusion Segregation Modelmentioning

confidence: 99%

River-bed armouring as a granular segregation phenomenon

et al. 2017

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“…One possible explanation is the existence of an effective surface tension σ at the interface of each stripe where σ increases with the difference between small and large particle diameters d l − d s [50]. It is always the stripe with the larger (d l − d s ) and therefore the larger σ which dissolves.…”

Section: Potential Mechanism Driving the Flow During Coarseningmentioning

confidence: 99%

The mechanism of long-term coarsening of granular mixtures in rotating drums

2015

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Three fundamental segregation and pattern formation processes are known in granular mixtures in a rotating cylindrical drum: radial segregation, axial banding, and coarsening of the band pattern. While the mechanism for the first effect is well understood and for the second effect, several models have been proposed, the long-term coarsening mechanism remained unexplained so far. We demonstrate that the unidirectional flow between the bands in an axially segregated pattern is driven by small differences in size of the small beads at the band edges. Due to a process of microsegregation inside each band of small particles, which was so far unrecognized, this difference in diameter will be effective in all experiments with polydisperse beads. In consequence the stability of individual bands can be easily controlled by minor alterations of their composition. Our results make evident that a new mechanism as the driving force behind the axial particle flow has to be sought. We suggest possible hypotheses for such a mechanism.

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Granular segregation in dense systems: the role of statistical mechanics and entropy

Cited by 2 publications

References 57 publications

River-bed armouring as a granular segregation phenomenon

River-bed armouring as a granular segregation phenomenon

The mechanism of long-term coarsening of granular mixtures in rotating drums

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