Hydrodynamic diffusivity of spherical particles in polymer solution |
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Authors: | Sangkyung Kim Minsoo Han Chongyoup Kim |
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Institution: | (1) Department of Polymer Engineering Chungnam National University 220 Goong-dong, Yoosong-goo Taejeon 305-764, Korea e-mail: cykim@hanbat.chungnam.ac.kr, KR |
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Abstract: | In this research experiments were performed to examine the hydrodynamic diffusion of spherical particles in a highly filled
suspension. The suspension consisted of nearly monodisperse polymethylmethacrylate spheres in a density matched polymer solution.
The polymer solution was prepared by dissolving 0–700 ppm of polyacrylamide in a mixture of ethyleneglycol and glycerine.
The polymer solution did not show appreciable shear thinning. The particle loading was varied from 30 to 55%. The hydrodynamic
diffusivity was estimated by measuring the time-dependent viscosity when the suspension was subjected to a circular Couette
flow with an air bubble trapped under the rotor of the Couette apparatus. The results show that the dimensionless diffusivity
(D/γ˙a
2) of particles in polymer solution is not proportional to shear rate (γ˙), as in the case of a Newtonian fluid, but that it
decreases with increasing shear rate. The diffusivity also decreases with increasing polymer concentration. It is suggested
that the elongational thickening behaviour and the increased lubrication force due to the first normal stress difference may
be responsible for the reduction of diffusivity in the polymer solution.
Received: 18 January 2000 Accepted: 6 April 2000 |
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Keywords: | Couette flow Particle-particle interaction First normal stress difference Elongational thickening |
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