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Imagerie ultrasonore dans les matériaux mous

Abstract : Soft matter scientists are dedicated to studying the properties of complex fluids. Complex fluids differ from simple fluids in that they possess a microstructure resulting from the particular arrangement of mesoscopic elements which constitute the material (aggregates of carbon black particles, entangled polymers, micelles of surfactant molecules, etc.). Peculiar flow behaviors in complex fluids, such as heterogeneous flows, arise from the coupling between microstructure and flow. Understanding these non-equilibrium states and the associated dynamics is both of industrial and fundamental interest. Rheology in a Taylor-Couette cell is a wide-spread technique for investigating the deformation and flow of complex fluids. However, this method is mostly blind to heterogeneous flows as it only provides a global description of the flow. To overcome this problem, an ultrasonic imaging technique has been combined with classical rheology. This local visualisation has allowed us to study the inertial Taylor-Couette instability in Newtonian fluids, elastic instabilities in viscoelastic fluids (polymers and micellar solutions), the fluidisation of yield stress fluids (carbon black gels, carbopol microgels and emulsions) and finally the failure of protein gels under stress. In all these cases we evidence a coexistence between different flow-induced states and revisit global rheological approaches through local characterizations of deformation and velocity fields.
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Submitted on : Friday, October 10, 2014 - 10:27:24 AM
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  • HAL Id : tel-01073593, version 1

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Christophe Perge. Imagerie ultrasonore dans les matériaux mous. Autre [cond-mat.other]. Ecole normale supérieure de lyon - ENS LYON, 2014. Français. ⟨NNT : 2014ENSL0913⟩. ⟨tel-01073593⟩

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