What mechanism governs slow flows of granular media? Microscopically, the grains experience enduring frictional contacts in these flows. However, a straightforward translation to a macroscopic frictional rheology, where the shear stresses are proportional to the normal stresses with a rate-independent friction coefficient, fails to capture important aspects of slow granular flows. There is now overwhelming evidence that agitations, tiny fluctuations of the grain positions, associated with large fluctuation of their contact forces, play a central role for slow granular flows. These agitations are generated in flowing regions, but travel deep inside the quiescent zones, and lead to a nonlocal rheology.
Quel est le mécanisme qui gouverne les écoulements lents d'un milieu granulaire ? À l'échelle microscopique, les grains sont soumis à des contacts frottants. Cependant, une interprétation directe de ces écoulements par une rhéologie macroscopique, dans laquelle les contraintes de cisaillement seraient proportionnelles aux contraintes normales avec un coefficient de frottement indépendant de la vitesse, ne permet pas de reproduire certaines propriétés importantes des écoulements lents. Il est maintenant clair que, lorsqu'elles sont associées à de grandes fluctuations des forces de contact, de très petites fluctuations des positions des grains jouent un rôle capital dans ces écoulements. Bien que l'agitation des grains provienne de zones en mouvement, elle pénètre profondément dans les régions inactives, donnant ainsi naissance à une rhéologie non locale.
Mots-clés : Écoulements granulaires lents, Rhéologie, Modèles non locaux, Agitation granulaire
Martin van Hecke 1
@article{CRPHYS_2015__16_1_37_0,
author = {Martin van Hecke},
title = {Slow granular flows: {The} dominant role of tiny fluctuations},
journal = {Comptes Rendus. Physique},
pages = {37--44},
publisher = {Elsevier},
volume = {16},
number = {1},
year = {2015},
doi = {10.1016/j.crhy.2014.11.004},
language = {en},
}
Martin van Hecke. Slow granular flows: The dominant role of tiny fluctuations. Comptes Rendus. Physique, Granular physics / Physique des milieux granulaires, Volume 16 (2015) no. 1, pp. 37-44. doi : 10.1016/j.crhy.2014.11.004. https://comptes-rendus.academie-sciences.fr/physique/articles/10.1016/j.crhy.2014.11.004/
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