Microrheology to probe non-local effects in dense granular flows
Physique et Mécanique des Milieux Hétérogènes, UMR 7636 ESPCI - CNRS - Univ. Paris-Diderot - Univ. P.M. Curie 10 rue Vauquelin, 75005 Paris, France
Received: 6 August 2014
Accepted: 23 December 2014
A granular material is observed to flow under the Coulomb yield criterion as soon as this criterion is satisfied in a remote but contiguous region of space. We investigate this non-local effect using discrete element simulations, in a geometry similar, in spirit, to the experiment of Reddy et al. (Phys. Rev. Lett., 106 (2011) 108301): a micro-rheometer is introduced to determine the influence of a distant shear band on the local rheological behaviour. The numerical simulations recover the dominant features of this experiment: the local shear rate is proportional to that in the shear band and decreases (roughly) exponentially with the distance to the yield conditions. The numerical results are in quantitative agreement with the predictions of the non-local rheology proposed by the present authors (Phys. Rev. Lett., 111 (2013) 238301) and derived from a gradient expansion of the rheology $\mu[I]$ . The consequences of these findings for the dynamical mechanisms controlling non-locality are finally discussed.
PACS: 45.70.-n – Granular systems / 83.80.Fg – Granular solids / 47.57.Gc – Granular flow
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