Withdrawal of a fibre from a liquid-filled capillary tube. Preliminary numerical results

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

Tandil

Congreso; XIII Reunión sobre Recientes Avances en Física de Fluidos y sus Aplicaciones (FLUIDOS 2014); 2014

Instituto de Física "Arroyo Seco", Universidad Nacional del Centro de la Provincia de Buenos Aires

Dip-coating is a technological process where a solid substrate submerged in a liquid bath is withdrawn from it at a given speed. The characteristics of the resulting coating layer deposited on the substrate depends on the physicochemical parameters of the working solid and fluid, the geometry of the substrate, as well as the operative parameters of the withdrawal operation. The withdrawal at a constant speed of flat surfaces and fibres are probably the most studied examples of this process. In the case of fibres, a common technological approach is to withdraw the filament from a small circular orifice or from within a liquid-filled capillary tube. This setup has also been employed in different experimental measurements of the process. We model this problem by solving numerically the 2D axisymmetric Navier-Stokes equations. The Finite Element Method, combined with an Arbitrary Lagrangian-Eulerian scheme, allows us to solve the governing equations only in the liquid phase and determine the shape of the meniscus that forms between the internal wall of the capillary tube and the liquid layer coating the fibre. Our numerical results show that the thickness of the coating layer formed on the fibre decreases when either the confinement (measured as the ratio of fibre to capillary diameter) augments or the contact angle between the meniscus and the capillary wall reduces.