Department of Physics Papers

Document Type

Journal Article

Date of this Version

12-19-2016

Publication Source

Physical Review E

Volume

94

Issue

6

Start Page

062609-1

Last Page

062609-10

DOI

10.1103/PhysRevE.94.062609

Abstract

Understanding the dynamics of fluid-driven sediment transport remains challenging, as it occurs at the interface between a granular material and a fluid flow. Boyer, Guazzelli, and Pouliquen [Phys. Rev. Lett.107, 188301 (2011)] proposed a local rheology unifying dense dry-granular and viscous-suspension flows, but it has been validated only for neutrally buoyant particles in a confined and homogeneous system. Here we generalize the Boyer, Guazzelli, and Pouliquen model to account for the weight of a particle by addition of a pressure P0 and test the ability of this model to describe sediment transport in an idealized laboratory river. We subject a bed of settling plastic particles to a laminar-shear flow from above, and use refractive-index-matching to track particles' motion and determine local rheology—from the fluid-granular interface to deep in the granular bed. Data from all experiments collapse onto a single curve of friction μ as a function of the viscous number Iv over the range 3 × 10−5Iv ≤ 2, validating the local rheology model. For Iv < 3 × 10−5, however, data do not collapse. Instead of undergoing a jamming transition with μ → μs as expected, particles transition to a creeping regime where we observe a continuous decay of the friction coefficient μ ≤ μs as Iv decreases. The rheology of this creep regime cannot be described by the local model, and more work is needed to determine whether a nonlocal rheology model can be modified to account for our findings.

Copyright/Permission Statement

© 2016 American Physical Society. You can view the original article at: https://journals.aps.org/pre/abstract/10.1103/PhysRevE.94.062609

Keywords

research areas, Flow confinement, Free-surface flows, granular flows, multiphase flows, rheology, sediment transport, viscoplasticity

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Date Posted:11 October 2017

This document has been peer reviewed.