Frédéric Blanc has been awarded by the French Group of Rheology for his PhD thesis. This study, which is part of the "Local rheology of concentrated suspensions" project and supervised by Élisabeth Lemaire and François Peters, dealt with rheology and micro-structure of non-brownian, concentrated, suspensions. For more information on this research activity and on related works, please have a look at the page of the group Suspensions Rheology. The abstract of this PhD work is available below. The Thesis Prize award ceremony took place during the annual congress of the GFR, Pau (France), 29th to 31st of October 2012.
Abstract of the thesis :
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 when the volume fraction approaches the packing fraction , the minimum viscosity scales as . 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.
The manuscript is available here (in french).
Fluides & Matériaux Complexes, Doctorants/Post-doctorants, Rhéologie des Suspensions
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