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17 juin 2019: 1 événement

  • Séminaires Invités

    Lundi 17 juin 14:00-15:30 - Annie Colin - ESPCI

    Coating of Yield Stress Fluids

    Résumé : We study the thickness of the coating that results from dipping a rod into bath of yield-stress liquid or after scrapping an yield stress fluid with an elastic wiper moved at a velocity V on a wetting surface. These geometries are widely used in cosmetic applications. In both cases we will show that the behavior is very different from that of a simple fluid.
    In the dip coating geometry, the coating thickness is observed to depend non-linearly on both geometrical conditions and fluid properties. When the yield-stress is large in comparison with the capillary pressure, the proximity of the stationary wall has a profound effect on the coating thickness. Strikingly, the thickness is found to be solely governed by the fluid flow inside the bath, which is obtained using the conservation of mass condition and the boundary conditions. A good agreement between experiments (thickness, velocity profile) and theory is obtained. These findings can be used to optimize the coating thickness in industrial applications.
    In the context of doctor blade geometry, we highlight a particular instability linked to the flow of fluid in the reservoir part.

    contact : Jean-Louis Barrat

    Lieu : LIPhy, conference room - 140 Avenue de la Physique 38402 Saint Martin d’Hères

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