Relevance of visco-plastic theory in a multi-directional inhomogeneous granular flow

Cortet, Pierre-Philippe; Bonamy, Daniel; Daviaud, François; Dauchot, Olivier; Dubrulle, Bérengère; Renouf, Mathieu

doi:10.1209/0295-5075/88/14001

Cited by 33 publications

(29 citation statements)

References 26 publications

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“…In the past decade, a local rheology emerges based on a unique relation of the friction coefficient µ with the socalled inertial number I corresponding to the shear rate made dimensionless with confining pressure and density [1,2]. This rheology works quite well by rescaling various experimental and numerical data into a consistent picture for parallel flows -such as Couette flows or flows down inclines -or weakly non parallel flows in a wide range of flow rates [1,3,4]. Nevertheless, this local description falls short of describing non-parallel flows where the streamlines are far from parallel and also quasi-static regimes close to the "liquid-solid" transition [5].…”

Section: Introductionmentioning

confidence: 99%

Local rheological measurements in the granular flow around an intruder

et al. 2016

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The rheological properties of granular matter within a two-dimensional flow around a moving disk is investigated experimentally. Using a combination of photoelastic and standard tessellation techniques, the strain and stress tensors are estimated at the grain scale in the time-averaged flow field around a large disk pulled at constant velocity in an assembly of smaller disks. On the one hand, one observes inhomogeneous shear rate and strongly localized shear stress and pressure fields. On the other hand, a significant dilation rate, which has the same magnitude as the shear strain rate, is reported. Significant deviations are observed with local rheology that justify the need of searching for a non-local rheology.

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Section: Introductionmentioning

confidence: 99%

Local rheological measurements in the granular flow around an intruder

et al. 2016

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“…A large body of work in the last decade has been devoted to the so-called µ(I) rheology [4,10]. While this rheology seems to work well (and should be probably better referred to) as an empirical, macroscopic scaling law, its colinear extension to 3D [11] was shown to have some drawbacks for complex flows, particularly when approaching the quasistatic regime of flow [12,13,6]. These problems seem to be related to the local nature of the µ(I) rheology and motivated research on nonlocal models of granular flows such as fluidity-based models [14][15][16][17] and models inspired by kinetic theories [18][19][20].…”

Section: Introductionmentioning

confidence: 99%

Torsional shear flow of granular materials: shear localization and minimum energy principle

Artoni¹,

Richard²

2016

Comp. Part. Mech.

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The rheological properties of granular matter submitted to torsional shear are investigated numerically by means of Discrete Element Method. The shear cell is made of a cylinder filled by grains which are sheared by a bumpy bottom and submitted to a vertical pressure which is applied at the top. Regimes differing by their strain localization features are observed. They originate from the competition between dissipation at the sidewalls and dissipation in the bulk of the system. The effects of the (i) the applied pressure (ii) sidewall friction and (iii) angular velocity are investigated. A model, based on the purely local µ(I)-rheology and a minimum energy principle is able to capture the effect of the two former quantities but unable to account the effect of the latter. Although, an ad-hoc modification of the model allows to reproduce all the numerical results, our results point out the need for an alternative rheology.

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“…We then compute the strain tensor ǫ and the stress tensor σ fields at the grain scale [28,[33][34][35][36]. Having checked that these tensors share the same eigenvectors [37], we restrict the analysis to their first and second invariants : the di-…”

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confidence: 99%

Shear Modulus and Dilatancy Softening in Granular Packings above Jamming

2014

Self Cite

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We investigate experimentally the mechanical response to shear of a monolayer of bi-disperse frictional grains across the jamming transition. We inflate an intruder inside the packing and use photo-elasticity and tracking techniques to measure the induced shear strain and stresses at the grain scale. We quantify experimentally the constitutive relations for strain amplitudes as low as 10 −3 and for a range of packing fractions within 2% variation around the jamming transition. At the transition strong nonlinear effects set in : both the shear modulus and the dilatancy shear-soften at small strain until a critical strain is reached where effective linearity is recovered. The scaling of the critical strain and the associated critical stresses on the distance to jamming are extracted. We check that the constitutive laws, together with mechanical equilibrium, correctly predict to the observed stress and strain profiles. These profiles exhibit a spatial crossover between an effective linear regime close to the inflater and the truly nonlinear regime away from it. The crossover length diverges at the jamming transition. Introduction. -Understanding the mechanical properties of dense packings of athermal particles, such as grains, foams and emulsions, remains a conceptual and practical challenge. When decreasing the packing fraction φ, these intrinsically out-of-equilibrium systems lose their rigidity at the so-called jamming transition, φ = φ J , when the confining pressure approaches zero and the particles deformations vanish [1][2][3][4]. In the case of frictionless spheres [2,3], the loss of mechanical stability coincides with the onset of isostaticity : the average number of contacts z decreases to its isostatic value, for which the number of geometrical and mechanical equilibrium constraints exactly match the number of degrees of freedom. Approaching the transition, the material becomes more and more fragile [5], and its linear response, dominated by floppy modes [6], exhibits critical scaling [2][3][4]7].

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Relevance of visco-plastic theory in a multi-directional inhomogeneous granular flow

Cited by 33 publications

References 26 publications

Local rheological measurements in the granular flow around an intruder

Local rheological measurements in the granular flow around an intruder

Torsional shear flow of granular materials: shear localization and minimum energy principle

Shear Modulus and Dilatancy Softening in Granular Packings above Jamming

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