Title: Three-dimensional continuum modeling of dense granular flow

Author (Invited): David Henann, Brown University

Abstract:

Dense, dry granular flows display many manifestations of grain-size dependence, or nonlocality, in which the finite-size of grains has an observable impact on flow phenomenology. These behaviors have made the formulation of an accurate continuum model for dense granular flow particularly difficult. We present a three-dimensional, continuum model for dry, steady flow, based on the nonlocal fluidity concept, aimed at filling this need. The key ingredient of the model is a grain-size-dependent, nonlocal contribution, in which flow at a point is affected by both the local stress as well as the flow in neighboring material. We then show that the model is capable of describing several distinct examples of grain-size dependent phenomenology: 1 - The grain-size-dependence of shear band widths in inhomogeneous, boundary-driven flow, such as annular shear and split-bottom shear flow, 2 - The concurrence of a rate-dependent, rapidly flowing layer on top of a rate-independent creeping bed in gravity-driven heap flows, and 3 - The apparent change in the rheology at a point induced by far-away shear deformation - termed the "secondary rheology."