Physics
Granular bed consolidation, creep, and armoring under subcritical fluid flow
Document Type
Article
Abstract
We show that a freshly sedimented granular bed settles and creeps forward over extended periods of time under an applied hydrodynamic shear stress which is below the critical value for bedload transport. The rearrangements are found to last over a timescale which is millions of times the sedimentation timescale of a grain in the fluid. Compaction occurs uniformly throughout the bed, but creep is observed to decay exponentially with depth and decreases over time. The granular volume fraction in the bed is found to increase logarithmically, saturating at the random close packing value φrcp≈0.64, while the surface roughness is observed to remain essentially unchanged. We demonstrate that an increasingly higher shear stress is required to erode the bed, after a subcritical shear is applied, which results in an increase in its volume fraction. Thus, we find that bed armoring occurs due to a deep shear-induced relaxation of the bed toward the volume fraction associated with the glass transition.
Publication Title
Physical Review Fluids
Publication Date
7-2018
Volume
7
Issue
3
ISSN
2469-990X
DOI
10.1103/PhysRevFluids.3.074305
Keywords
geophysics, granular compaction, granular flows
Repository Citation
Allen, Benjamin and Kudrolli, Arshad, "Granular bed consolidation, creep, and armoring under subcritical fluid flow" (2018). Physics. 94.
https://commons.clarku.edu/faculty_physics/94
Cross Post Location
Student Publications
