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Article Dans Une Revue Annales De Physique Année : 1998

Hydrodynamic coating of a fiber

Le mouillage dynamique des fibres

Résumé

We discuss how a solid (especially a fiber) is coated when drawn out of a bath of liquid. 1. For slow withdrawals out of pure viscous liquids, the data are found to be fitted by the famous Landau law: then, the coating results from a balance between viscosity and capillarity. For quicker withdrawals, the thickness of the entrained film suddenly diverges, at a velocity on order 1 m/s. Inertia is shown to be responsible for this effect. At still higher velocities, the thickness decreases with the velocity because the solid can only entrain the viscous boundary layer. 2. For complex fluids, surface effects are found in the low velocity regime: out of a surfactant solution, films are thicker than predicted by Landau, by a factor of order 2. The thickening factor is shown to be fixed by the Marangoni flow due to the presence of surfactants; out of an emulsion, the film can be enriched with oil, which can be understood by a simple model of capture; out of a polymer solution, a strong swelling of the film is observed if normal stresses are present. Hence, the problem has two families of solution: (i) at low velocity, the thickness of the layer is fixed by a balance between viscous and surface forces and thus is sensitive to the presence of surfactants, or other heterogeneities; (ii) at high velocity, inertia must be considered and the film thickness is fixed by the bulk properties of the liquid (density and viscosity). In these regimes, it is not affected by the presence of surfactants in the bath.
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Dates et versions

hal-01652392 , version 1 (08-11-2019)

Identifiants

Citer

D Quere, Alain de Ryck. Hydrodynamic coating of a fiber. Annales De Physique, 1998, 23 (1, SI), pp.1+. ⟨10.1051/anphys:199801001⟩. ⟨hal-01652392⟩
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