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Axisymmetric gravity currents of power-law fluids over a rigid horizontal surface

Published online by Cambridge University Press:  28 January 2013

Roiy Sayag  and
M. Grae Worster
Roiy Sayag*
Affiliation:
Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge CB3 0WA, UK
M. Grae Worster
Affiliation:
Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge CB3 0WA, UK
*
†Email address for correspondence: rs620@cam.ac.uk
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Abstract

We analyse axisymmetric gravity currents of power-law fluids theoretically and experimentally. We use aqueous suspensions of Xanthan gum in laboratory experiments of constant-volume and constant-flux release to resolve the rheological parameters of the fluid, which we then compare with measurements made using a strain-controlled rheometer. We find that the constant-volume release of highly shear-thinning fluids involves an early-time evolution dominated by inertia, and non-convex free surfaces that make the application of similarity solutions of the late-time viscously dominated evolution inefficient at resolving material properties. In contrast, constant-flux release of the same fluids can be viscously dominated and consistent with the self-similar solution from early in the evolution, which makes it a more useful method for measuring rheological parameters.

JFM classification

Complex Fluids: Complex Fluids Geophysical and Geological Flows: Geophysical and Geological Flows Non-Newtonian Flows: Non-Newtonian Flows
Type
Rapids
Information
Journal of Fluid Mechanics , Volume 716 , 10 February 2013 , R5
Copyright
©2013 Cambridge University Press

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Sayag and Worster supplementary movie

This video shows the constant-volume release of a shear-thinning fluid (aqueous suspension of Xanthan gum), captured in 2000 frames per second. The volume of 490 cm3 is initially contained in a cylinder 64 mm in diameter. The cylinder is lifted by a pneumatic actuator vertically up above a flat surface, releasing the fluid

Download Sayag and Worster supplementary movie(Video)
Video 11.8 MB