Particle migration in a concentrated suspension flowing between rotating parallel plates: Investigation of diffusion flux coefficients

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Abstract
This paper reports an experimental and numerical study conducted to investigate the behavior of macroscopic monomodal concentrated suspensions (40%) undergoing a creeping torsional flow between two rotating plates. An experimental technique based on the detection of tracers by measurement of light absorption is developed and used to quantify the time evolution of the particles concentration profiles. Contrarily to results reported in the literature, an outward migration of the particles is observed. This shear-induced migration is confirmed by viscometric measurements where an increase in the apparent viscosity of the suspension has been observed for long periods of shear. Moreover, this increase is found to depend solely on the value of the applied strain, which is consistent with a shear-induced migration phenomenon. Experimental results are reproduced using a semi-quantitative model involving the balance of three diffusion fluxes induced, respectively, by the gradient of viscosity (Jη), the gradient of...

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