Liquid transfer between a single cavity and a moving plate. Interface-tracking versus interface-capturing approaches

A. BRONDINO; M.S. CARVALHO; D.M. CAMPANA; S. UBAL

La Plata

Congreso; XIV Reunión sobre Avances en Física de Fluidos y sus Aplicaciones; 2016

IFLYSIB ? UNLP

Gravure printing is one of the most promising technologies for high volume production of printed electronics and microscale films and devices. As in many printing processes, the essential aspect is the liquid transfer between surfaces in relative movement. This transfer involves the formation of a liquid bridge, which eventually breaks under an extensional motion, and the displacement of the contact lines on the surfaces. In this work, we studythe transfer of a liquid initially contained in a fixed axisymmetric trapezoidal cavity to a moving plate. The analysis is made using a kinematic description of the stretching (vertical) velocity of the top-plate relative to the cavity, based on the kinematics of a roll-to-roll system [1]. We model the fluid flow by solving the Navier-Stokes equations with the finite element method on a moving/deforming mesh that follows the plate displacement. An interface-capturing technique, based on the level-set approach, involves the computation of a scalar field that defines the two phases present in the problem (air and liquid). In order to validate our results we compared them with previous works based on an interface-tracking technique [1, 2], which has been widely validated. With an appropriate selection of the numerical parameters and mesh refinement, the liquid volume extracted from the cavity (transferred liquid fraction φ) and the contact line position (shape of the printed pattern) arein excellent agreement with those reported previously for a set of parameters of the printing process (capillary number, filling fraction, contact angle, etc.). Basically, our results follow the same trends reported by Dodds and coworkers [3], who considered a constant stretching velocity for the plate. As a drawback, since the interface is defined as an iso-surface  (level-set) of the scalar field, the evaluation of the surface curvature (and the surface pressure jump) usually is not as accurate as for interface-tracking methods. As advantage, with this approach is possible to handle large interface deformation and solve the flow dynamics after the breakup of the liquid bridge.In the future we plan to study the interaction between two or more cavities, which may involve complex processes as droplet formation, coalescence and air entrapment, among others.