Revealing the Structure of a Granular Medium through Ballistic Sound Propagation

Lherminier, Sébastien; Planet, Ramon; Simon, Gregory E.; Vanel, Loïc; Ramos, Osvanny

doi:10.1103/physrevlett.113.098001

Cited by 26 publications

(32 citation statements)

References 32 publications

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“…Their long-time motion may be modeled as vertically isotropic and constant diffusion. Short-time dynamics show that creeping grains are caged, and indicate that their motion is likely induced by long-range transmission of forces through the granular contact network 46 , 47 . This may be why creep motion is independent of shear rate, at least for the range of Shields stresses examined here.…”

Section: Discussionmentioning

confidence: 98%

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: Discussionmentioning

confidence: 98%

River-bed armouring as a granular segregation phenomenon

et al. 2017

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“…4(b). We observe a continuous variation from the known 1/6 exponent [6,15,31] to a near-zero value for a high confinement pressure. These findings indicate that the medium undergoes a transition from a nonlinear propagation regime to a linear propagation regime, where the propagation velocity does not depend on the amplitude of the impulse [32].…”

Section: A Pulse Propagation Speedmentioning

confidence: 89%

Mechanical impulse propagation in a three-dimensional packing of spheres confined at constant pressure

2016

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Mechanical impulse propagation in granular media depends strongly on the imposed confinement conditions. In this work, the propagation of sound in a granular packing contained by flexible walls that enable confinement under hydrostatic pressure conditions is investigated. This configuration also allows the form of the input impulse to be controlled by means of an instrumented impact pendulum. The main characteristics of mechanical wave propagation are analyzed, and it is found that the wave speed as function of the wave amplitude of the propagating pulse obeys the predictions of the Hertz contact law. Upon increasing the confinement pressure, a continuous transition from nonlinear to linear propagation is observed. Our results show that in the low-confinement regime, the attenuation increases with an increasing impulse amplitude for nonlinear pulses, whereas it is a weak function of the confinement pressure for linear waves.

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“…For example, the electrical conductivity of a granular bed strongly depends not only on the actual strength of the contacts [1], but also on the structure of the contact network and the presence of paths of strong contacts [2]. Similarly, the elastic properties of these systems are very sensitive to the characteristic of underlying force network [3,4], to the degree that different packing structures can be distinguished by their response to sound propagation [5].…”

Section: Introductionmentioning

confidence: 99%

Structure of force networks in tapped particulate systems of disks and pentagons. I. Clusters and loops

et al. 2016

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The force network of a granular assembly, defined by the contact network and the corresponding contact forces, carries valuable information about the state of the packing. Simple analysis of these networks based on the distribution of force strengths is rather insensitive to the changes in preparation protocols or to the types of particles. In this and the companion paper [Kondic et al., Phys. Rev. E 93, 062903 (2016)10.1103/PhysRevE.93.062903], we consider two-dimensional simulations of tapped systems built from frictional disks and pentagons, and study the structure of the force networks of granular packings by considering network's topology as force thresholds are varied. We show that the number of clusters and loops observed in the force networks as a function of the force threshold are markedly different for disks and pentagons if the tangential contact forces are considered, whereas they are surprisingly similar for the network defined by the normal forces. In particular, the results indicate that, overall, the force network is more heterogeneous for disks than for pentagons. Such differences in network properties are expected to lead to different macroscale response of the considered systems, despite the fact that averaged measures (such as force probability density function) do not show any obvious differences. Additionally, we show that the states obtained by tapping with different intensities that display similar packing fraction are difficult to distinguish based on simple topological invariants.

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Revealing the Structure of a Granular Medium through Ballistic Sound Propagation

Cited by 26 publications

References 32 publications

River-bed armouring as a granular segregation phenomenon

River-bed armouring as a granular segregation phenomenon

Mechanical impulse propagation in a three-dimensional packing of spheres confined at constant pressure

Structure of force networks in tapped particulate systems of disks and pentagons. I. Clusters and loops

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