Wall effects on the sedimentation of a sphere in power-law fluids

Document Type

Conference Proceeding

Publication Date

1-1-2017

Abstract

In this work, wall retardation effect on the terminal velocity of a sphere falling at the axis of cylindrical tubes filled with power-law fluids has been studied numerically. The results reported herein encompass the following ranges of conditions: power-law index, 0.2 ≤ n ≤ 2; Reynolds number, 0.01 ≤ RePL ≤ 100 and sphere-to-tube diameter ratio, 0.5 ≤ λ ≤ 0.95. Limited results were also obtained for λ < 0.5 for the purpose of validation of the present results. The presence of the confining walls retards the sedimentation of a sphere and this effect gets accentuated with the increasing value of λ. Indeed, at fixed values of RePL and n, the drag coefficient can increase by more than a factor of 10 in highly shear-thinning fluids (n = 0.2) whereas the corresponding increase is of the order of 1000 in shear-thickening fluids as the value of λ is increased from λ = 0.5 to λ = 0.95. Broadly, the wall effect diminishes with the increasing Reynolds number and/or decreasing power-law index. However, the extent of retardation of sphere increases with the increasing value of λ.

Identifier

85021837980 (Scopus)

Publication Title

20th International Conference on Hydrotransport

First Page

429

Last Page

442

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