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

Published online by Cambridge University Press:  17 August 2005

L. A. MONDY
Affiliation:
Sandia National Laboratories, Albuquerque NM 87185-0834, USA
A. M. GRILLET
Affiliation:
Sandia National Laboratories, Albuquerque NM 87185-0834, USA
G. PACHECO
Affiliation:
Sandia National Laboratories, Albuquerque NM 87185-0834, USA Present address: Honeywell, San Diego, CA 92173, USA.
J. HENFLING
Affiliation:
Sandia National Laboratories, Albuquerque NM 87185-0834, USA
M. S. INGBER
Affiliation:
Department of Mechanical Engineering, University of New Mexico, Albuquerque NM 87131, USA
A. L. GRAHAM
Affiliation:
Los Alamos National Laboratory, Los Alamos, NM 87545, USA
H. BRENNER
Affiliation:
Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge MA 02139, USA

Abstract

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.

Type
Papers
Copyright
© 2005 Cambridge University Press

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