Inertia effects on the dip-coating of fibers. Numerical analysis

DIEGO M. CAMPANA; SEBASTIÁN UBAL; MARÍA D. GIAVEDONI; FERNANDO A. SAITA

Ciudad Autónoma de Buenos Aires

Congreso; XII Reunión de Fluidos y sus Aplicaciones (Fluidos 2012); 2012

Grupo de Medios Porosos (FI-UBA), Carlos Perazzo (U. Favaloro)

Dip-coating is the process by which a thin layer of liquid is deposited on a given substrate, as it is withdrawn from a pool of coating liquid. Conceptually simple, the process is commonly employed to coat galvanised metal sheets and wires, hoses and optical fibers, for example. The two geometrical configurations most widely studied theoretically are the plane and cylindrical substrates, the latter being the subject of this work. Since the pioneer papers by Landau and Levich (1942) and Derjaguin (1943), considerable literature has been published. White and Tallmadge (1966) presented an adaptation of the lubrication analysis by Landau and Levich (1942) to the cylindrical configuration. The film thickness predicted in this paper is valid only for the so-called visco-capillary regime. However, when inertia effects become important, the deposited film becomes thicker than the one predicted by White and Tallmadge (1966), as observed experimentally by de Ryck and Quéré (1996) and Rebouillat et al. (2002). In this work, we study numerically the dip-coating of fibers for the visco-inertial regime. Our numerical predictions, obtained for the same parameters employed in the experiments carried out by de Ryck and Quéré (1996) and Rebouillat et al. (2002), show a very good agreement with the film thicknesses measured by these authors, giving also a detailed description of the flow fields.