ISSN:
1089-7666
Source:
AIP Digital Archive
Topics:
Physics
Notes:
A novel theoretical scheme is presented, which permits measurements of the so-called shear-induced diffusivity in concentrated suspensions to be made based upon long-time data collected in a two-cylinder Couette device. For this purpose the motion of a single (labeled) suspended particle is analyzed as the suspension, which fills the region between the two concentric cylinders, is sheared by rotating the outer cylinder. As the particle samples all radial coordinates as a result of its lateral self-diffusivity caused by collisions with other suspended particles, its azimuthal coordinate increases. For long times, a Taylor–Aris-type dispersion analysis shows that both the mean angular position 〈θ〉 and the mean square deviation 〈(θ−〈θ〉)2〉 of the labeled particle grow linearly in time. The two coefficients that govern these linear growths are the mean angular velocity Ω¯* and twice the mean angular dispersivity D¯@B|θ, which are calculated herein as functions of the cylinder radii, particle size, rotation speed, and the shear-induced diffusivity. Measurements of the latter of these, based upon the outlined long-time data, can thus be made more accurately than those previously possible on the basis of short-time analyses that neglected the presence of the walls of the Couette device and its curved geometry.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.866985
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