Apparent slip at the surface of a ball spinning in a concentrated suspension

The couple on a ball rotating relative to an otherwise quiescent suspension of comparably-sized, neutrally buoyant spheres is studied both experimentally and numerically. Apparent ‘slip’ relative to the analytical solution for a sphere spinning in a Newtonian fluid (based upon the viscosity of the s...

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Bibliographic Details
Published in:Journal of fluid mechanics 2005-09, Vol.538, p.377-397
Main Authors: MONDY, L. A., GRILLET, A. M., PACHECO, G., HENFLING, J., INGBER, M. S., GRAHAM, A. L., BRENNER, H.
Format: Article
Language:English
Subjects:
Cross-disciplinary physics: materials science
rheology
Exact sciences and technology
Heterogeneous liquids: suspensions, dispersions, emulsions, pastes, slurries, foams, block copolymers, etc
Material form
Physics
Rheological measurements
Rheology
Techniques and apparatus
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Summary:The couple on a ball rotating relative to an otherwise quiescent suspension of comparably-sized, neutrally buoyant spheres is studied both experimentally and numerically. Apparent ‘slip’ relative to the analytical solution for a sphere spinning in a Newtonian fluid (based upon the viscosity of the suspension) is determined in suspensions with volume fractions $c$ ranging from 0.03 to 0.50. This apparent slip results in a decrease of the measured torque on the spinning ball when the radius of the ball becomes comparable with that of the suspended spheres. Over the range of our data, the slip becomes more pronounced as the concentration $c$ increases. At $c\,{=}\,$0.25, three-dimensional boundary-element simulations agree well with the experimental data. Moreover, at $c\,{=}\,$0.03, good agreement exists between such calculations and theoretical predictions of rotary slip in dilute suspensions.
ISSN:0022-1120
1469-7645
DOI:10.1017/S0022112005005380