A hierarchy of granular continuum models: Why flowing grains are both simpleand complex
Author(s)Kamrin, Kenneth N
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ranular materials have a strange propensity to behave as either a complex media or a simple media depending on the precise question being asked. This review paper offers a summary of granular flow rheologies for well-developed or steady-state motion, and seeks to explain this dichotomy through the vast range of complexity intrinsic to these models. A key observation is that to achieve accuracy in predicting flow fields in general geometries, one requires a model that accounts for a number of subtleties, most notably a nonlocal effect to account for cooperativity in the flow as induced by the finite size of grains. On the other hand, forces and tractions that develop on macro-scale, submerged boundaries appear to be minimally affected by grain size and, barring very rapid motions, are well represented by simple rate-independent frictional plasticity models. A major simplification observed in experiments of granular intrusion, which we refer to as the ‘resistive force hypothesis’ of granular Resistive Force Theory, can be shown to arise directly from rate-independent plasticity. Because such plasticity models have so few parameters, and the major rheological parameter is a dimensionless internal friction coefficient, some of these simplifications can be seen as consequences of scaling.
DepartmentMassachusetts Institute of Technology. Department of Mechanical Engineering
EPJ Web of Conferences
Kamrin, Ken. “A Hierarchy of Granular Continuum Models: Why Flowing Grains Are Both Simple and Complex.” Edited by F. Radjai, S. Nezamabadi, S. Luding, and J.Y. Delenne. EPJ Web of Conferences 140 (2017): 01007 © 2017 The Authors, published by EDP Sciences
Final published version