Rhéologie et microstructure des suspensions concentrées non browniennes

Abstract : The subject of this thesis is an experimental study of the shear-induced microstructure in non-Brownian suspensions and its relation to the material rheological response, with a particular interest in the role played by the contact between particles. To this purpose, two experimental set-ups were developed. The first one, based on a Particle Image Velocimetry technique, allows local rheometry measurements through the determination of the velocity profile in the sheared suspension. In the second type of experiment, every single particle is tracked, making the shear-induced microstructure available. After a shear reversal, the measured viscosity undergoes a quick decrease before it increases again toward the stationary value. While the stationary viscosity scales as ( Φ*-Φ)-2 when the volume fraction Φ approaches the packing fraction Φ*, the minimum viscosity scales as ( Φ*-Φ)-1. These two different scalings are explained by the important role played by the contact between particles and the microstructure in the suspension rheology. In dilute suspensions, the microstructure, as measured by the pair distribution function, shows fore-aft asymmetry and a tilt angle with respect to the velocity axis. From this result, that is well explained by a model based on particle pair trajectories, we can conclude that contact occurs between the particles due to roughness. For larger concentrations, the depleted zone tilts toward the recession axis, and a high probability area appears in the velocity direction.
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Soft Condensed Matter. Université Nice Sophia Antipolis, 2011. French


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Submitted on : Thursday, January 12, 2012 - 3:30:48 PM
Last modification on : Thursday, January 19, 2012 - 9:28:02 AM

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Frédéric Blanc. Rhéologie et microstructure des suspensions concentrées non browniennes. Soft Condensed Matter. Université Nice Sophia Antipolis, 2011. French. <tel-00659207v2>

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