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Theses

Friction and jamming in dry granular flows

Abstract : The two subjects of this thesis are friction and jamming in dry granular flows. combining physical experiments and discrete numerical simulations, we study the rheological behaviour of model materials sheared between rough walls, in various geometries (plane shear cell, annular shear and inclined plane). We shox that the shear state of the granular material is entirely governed by the inertial dimensionless number I, related to the ratio between inertial and confinement forces. Weak (respectively large) values of I correspond to the quasi-static (respectively dynamic) regime. The constitutive law is then deduced from the measurement of the variation of dilatancy and effective friction with I. When the shear rate is controlled, we show that the transition between the quasi-static and the dynamic regimes is continuous. In this intermediate regime, the constitutive law does not depend on the mechanical characteristics of the grains (slightly or strongly dissipative) and remains qualitatively identical in the various shear geometries. Contrary to homogeneous flows, we notice a localisation of the shear whence the stress distribution is heterogenous. We observe that the flow becomes intermittent in the quasi-static regime. Conversely, when the shear stress is controlled, we show that the jamming transition between the quasi-static ant the dynamic regimes is discontinuous, hysteretic and presents strong similarities with the transition observed in thixotropic fluids (pastes, foams, etc.). The experiments, both in annular shear cell and down inclined plane, show that the range of shear rate cannot be reached in the steady state ("viscosity bifurcation"). Using discrete numerical simulations, we also show a discontinuous transition of the contact network during jamming. Then, we propose a model of the jamming, based on the trapping of the grains induced by the wall roughness. moreover we also show the interest of a nonlocal rheological model in the description of the jamming.
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https://pastel.archives-ouvertes.fr/pastel-00000946
Contributor : Ecole Des Ponts Paristech <>
Submitted on : Monday, December 20, 2004 - 8:00:00 AM
Last modification on : Monday, December 20, 2004 - 8:00:00 AM
Long-term archiving on: : Friday, October 19, 2012 - 11:35:23 AM

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  • HAL Id : pastel-00000946, version 1

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Frédéric da Cruz. Friction and jamming in dry granular flows. Engineering Sciences [physics]. Ecole des Ponts ParisTech, 2004. English. ⟨pastel-00000946⟩

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