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Microstructure of strongly sheared suspensions and its impact on rheology and diffusion

Published online by Cambridge University Press:  10 October 1997

JOHN F. BRADY
Affiliation:
Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA; e-mail: jfbrady@caltech.edu; jeff.morris@che.gatech.edu
JEFFREY F. MORRIS
Affiliation:
Present address: School of Chemical Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA. Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA; e-mail: jfbrady@caltech.edu; jeff.morris@che.gatech.edu

Abstract

The effects of Brownian motion alone and in combination with an interparticle force of hard-sphere type upon the particle configuration in a strongly sheared suspension are analysed. In the limit Pe→∞ under the influence of hydrodynamic interactions alone, the pair-distribution function of a dilute suspension of spheres has symmetry properties that yield a Newtonian constitutive behaviour and a zero self-diffusivity. Here, Pe=γ˛a2/2D is the Péclet number with γ˛ the shear rate, a the particle radius, and D the diffusivity of an isolated particle. Brownian diffusion at large Pe gives rise to an O(aPe−1) thin boundary layer at contact in which the effects of Brownian diffusion and advection balance, and the pair-distribution function is asymmetric within the boundary layer with a contact value of O(Pe0.78) in pure-straining motion; non-Newtonian effects, which scale as the product of the contact value and the O(a3Pe−1) layer volume, vanish as Pe−0.22 as Pe→∞.

Type
Research Article
Copyright
© 1997 Cambridge University Press

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