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9 avril 2021: 1 événement


  • Coating of complex fluids - Annie Colin

    Vendredi 9 avril 11:00-12:00 - Annie Colin - ESPCI Paris - Université PSL

    Coating of complex fluids - Annie Colin

    Résumé : In order to treat surfaces, thin layers of complex fluids, suspensions are deposited on surfaces. In this talk I will present two experimental geometries for deposition : Dip coating and a elastic blade. I will study both simple and complex fluids. The dip-coating process consists of withdrawing immersed objects from a liquid reservoir. After withdrawal, a significant layer of liquid remains on the object. Various industrial processes (food and beverage industry, automotive industry) use this technique to coat or treat surfaces. Recent studies have shown that the thickness of deposit is determined by the flow inside the reservoir for yield-stress fluids. This is different from the behavior of simple liquids for which the coating thickness is solely determined by the flow inside the meniscus. In this work, we re-examine this question and propose a complete phase diagram linking the Newtonian case and the yield-stress fluid case. We provide asymptotic scaling laws for extreme cases. A good agreement with experiments is obtained. The spreading of fluid by a deformable blade is also a common industrial problem, characteristic of elasto-hydrodynamic situations. Here, I will consider the case of a finite reservoir of liquid, emptying as the liquid is spread. I will evidence the role of a central the wetting length lw, which sets a boundary between the wet and dry parts of the blade. I will show that the deposited film thickness e depends quadratically with lw. We study this problem experimentally and numerically by integration of the elasto-hydrodynamic equations, and finally propose a scaling law model to explain how lw influences the spreading dynamics.This study is performed on Newtonian fluids but also on complex fluids.
    References :Retour ligne automatique
    Krapez, Marion, Anaïs Gauthier, Hamid Kellay, Jean-Baptiste Boitte,Retour ligne automatique
    Odile Aubrun, Jean-François Joanny, and Annie Colin. "Impact of theRetour ligne automatique
    Wetting Length on Flexible Blade Spreading." Physical Review LettersRetour ligne automatique
    125, no. 25 (2020) : 254506.
    Smit, Wilbert J., Christophe Kusina, Jean-François Joanny, and AnnieRetour ligne automatique
    Colin. "Stress Field inside the Bath Determines Dip Coating withRetour ligne automatique
    Yield-Stress Fluids in Cylindrical Geometry." Physical review lettersRetour ligne automatique
    123, no. 14 (2019) : 148002

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