Facial reconstruction

Search LJMU Research Online

Browse Repository | Browse E-Theses

A two-dimensional depth-averaged μ(I)-rheology for dense granular avalanches

Baker, JL, Barker, T and Gray, JMNT (2015) A two-dimensional depth-averaged μ(I)-rheology for dense granular avalanches. Journal of Fluid Mechanics, 787. pp. 367-395. ISSN 0022-1120

div-class-title-a-two-dimensional-depth-averaged-span-class-inlineformula-span-class-alternatives-img-class-inline-graphic-mathjax-alternative-mathjax-alt-graphic-mathjax-off-da.pdf - Published Version
Available under License Creative Commons Attribution.

Download (1MB) | Preview
Open Access URL: https://doi.org/10.1017/jfm.2015.684 (Published version)


Steady uniform granular chute flows are common in industry and provide an important test case for new theoretical models. This paper introduces depth-integrated viscous terms into the momentum-balance equations by extending the recent depth-averaged μ(I)-rheology for dense granular flows to two spatial dimensions, using the principle of material frame indifference or objectivity. Scaling the cross-slope coordinate on the width of the channel and the velocity on the one-dimensional steady uniform solution, we show that the steady two-dimensional downslope velocity profile is independent of scale. The only controlling parameters are the channel aspect ratio, the slope inclination angle and the frictional properties of the chute and the sidewalls. Solutions are constructed for both no-slip conditions and for a constant Coulomb friction at the walls. For narrow chutes, a pronounced parabolic-like depth-averaged downstream velocity profile develops. However, for very wide channels, the flow is almost uniform with narrow boundary layers close to the sidewalls. Both of these cases are in direct contrast to conventional inviscid avalanche models, which do not develop a cross-slope profile. Steady-state numerical solutions to the full three-dimensional μ(I)-rheology are computed using the finite element method. It is shown that these solutions are also independent of scale. For sufficiently shallow channels, the depth-averaged velocity profile computed from the full solution is in excellent agreement with the results of the depth-averaged theory. The full downstream velocity can be reconstructed from the depth-averaged theory by assuming a Bagnold-like velocity profile with depth. For wide chutes, this is very close to the results of the full three-dimensional calculation. For experimental validation, a laser profilometer and balance are used to determine the relationship between the total mass flux in the chute and the flow thickness for a range of slope angles and channel widths, and particle image velocimetry (PIV) is used to record the corresponding surface velocity profiles. The measured values are in good quantitative agreement with reconstructed solutions to the new depth-averaged theory.

Item Type: Article
Uncontrolled Keywords: 01 Mathematical Sciences; 09 Engineering; Fluids & Plasmas
Subjects: Q Science > QA Mathematics > QA75 Electronic computers. Computer science
Q Science > QC Physics
T Technology > TA Engineering (General). Civil engineering (General)
Divisions: Computer Science & Mathematics
Publisher: Cambridge University Press (CUP)
SWORD Depositor: A Symplectic
Date Deposited: 20 Mar 2023 12:57
Last Modified: 20 Mar 2023 12:57
DOI or ID number: 10.1017/jfm.2015.684
URI: https://researchonline.ljmu.ac.uk/id/eprint/19141
View Item View Item