Physics
Effective drag of a rod in fluid-saturated granular beds
Document Type
Article
Abstract
We measure the drag encountered by a vertically oriented rod moving across a sedimented granular bed immersed in a fluid under steady-state conditions. At low rod speeds, the presence of the fluid leads to a lower drag because of buoyancy, whereas a significantly higher drag is observed with increasing speeds. The drag as a function of the depth is observed to decrease from being quadratic at low speeds to appearing more linear at higher speeds. By scaling the drag with the average weight of the grains acting on the rod, we obtain the effective friction μe encountered over six orders of magnitude of speeds. While a constant μe is found when the grain size, rod depth, and fluid viscosity are varied at low speeds, a systematic increase is observed as the speed is increased. We analyze μe in terms of the inertial number I and viscous number J to understand the relative importance of inertia and viscous forces, respectively. For sufficiently high fluid viscosities, we find that the effect of varying the speed, depth, and viscosity can be described by the empirical function μe=μo+kJn, where μo is the effective friction measured in the quasistatic limit, and k and n are material constants. The drag is then analyzed in terms of the effective viscosity ηe and found to decrease systematically as a function of J. We further show that ηe as a function of J is directly proportional to the fluid viscosity and the μe encountered by the rod.
Publication Title
Physical Review E
Publication Date
8-7-2019
Volume
100
Issue
2
ISSN
2470-0045
DOI
10.1103/PhysRevE.100.022901
Keywords
wet granular materials, rheological properties
Repository Citation
Allen, Benjamin and Kudrolli, Arshad, "Effective drag of a rod in fluid-saturated granular beds" (2019). Physics. 90.
https://commons.clarku.edu/faculty_physics/90
Cross Post Location
Student Publications
