12/05/2023 – C. Barentin – Plastocapillarity: wetting of yield-stress fluids
Séminaire IUSTI – 12 mai 2023 – 11h salle 259
Plastocapillarity: wetting of yield-stress fluids
Catherine Barentin – ILM, Lyon
Yield-stress fluids such as emulsions, suspensions, gels or foams exhibit interesting mechanical properties depending on the applied stress. Indeed they behave like an elastic below a critical stress called “yield stress” and flow like a liquid above it. This intermediate behavior solid/liquid makes them particularly interesting for applications (food industry, cosmetics, building industry), but fundamentally difficult to describe.
In this seminar, I will study the wetting properties of yield stress fluids by performing three capillary experiments: a) capillary rise  , b) adhesion due to a capillary bridge  and c) spreading of a drop of a yied-stress fluid . In the case of simple fluids, such experiments are classical and the wetting laws (Jurin’s law or Young law) are well kown. Here I will study the influence of the yield stress on the final capillary rise or on the final contact angle. I will also show the strong impact of the dynamic history and of the boundary conditions . More importantly, I will show that exploring the competition between surface tension, which is an equilibrium property, and yield stress effects that often keep the system out of thermodynamic equilibrium due to a dynamic arrest is possible as soon as force balances are performed.
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