Wall roughness and nonlinear velocity profiles in granular shear flows
1 LMGC, UMR 5508 CNRS – Université de Montpellier, 163 rue Auguste Broussonnet, 34090 Montpellier, France
2 〈MSE〉 2, UMI 3466 CNRS-MIT, CEE, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge 02139, USA
3 LMT, ENS Paris-Saclay / CNRS / Univ. Paris-Saclay, 61 Av. du Président Wilson, 94235 Cachan Cedex, France
* e-mail: firstname.lastname@example.org
Published online: 30 June 2017
Inhomogeneous velocity profiles in granular flows are well known from both experiments and simulations, and considered as a hallmark of nonlocal behavior. By means of extensive contact dynamics simulations, we show that the sigmoidal velocity profiles in 2D flows of rigid disks are controlled by the roughness of driving boundary walls. We find that the velocity profile becomes linear for a critical value of wall roughness up to an exponential decay close to the walls with a characteristic length that does not depend on the flow thickness and rate. We describe the velocity profiles by introducing a state parameter that carries wall perturbation. By assuming that the local shear rate is a linear function of the state parameter, we obtain an analytical expression that fits velocity profiles. In this model, the nonlinear velocity profiles are explained in terms of the effects of wall roughness as boundary condition for the state parameter.
© The Authors, published by EDP Sciences, 2017
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