Three dimensional numerical simulations of the liquid transfer between a cavity and a moving roll

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

San Diego

Simposio; 17th International Coating Science and Technology Symposium (ISCST 2014); 2014

International Society of Coating Science and Technology / Association of International Metallizers, Coaters and Laminators

In this work we propose a full 3D model for the liquid transference between an engraved cavity and a moving substrate, which represents a simplification of the process taking place in a roll-to roll gravure printing system. The model is solved numerically with the finite elements method and the flow domain is discretized with an unstructured mesh. A robust fully coupled Arbitrary-Lagrangian-Eulerian technique is used to calculate the unknown three-dimensional flow domain, simultaneously with the flow variables. The relative velocity between the cavity and the substrate mimics this of a roll-to-roll system, presenting stretching, shearing and rotation. This motion promotes different curvatures between the front and rear parts of the 3D meniscus. The results suggest that the liquid fraction extracted from the cavity is a strong function of the Capillary number (Ca). At moderate values of Ca the contact line pins markedly on the cavity but slips easily on the moving plate, thus reducing the size of the drops left over it after the filament breakup. However, at low values of Ca, the contact lines have higher mobility and the pressure difference created by the non-symmetric meniscus drains completely the liquid outside the cavity. At that situation, half of the liquid volume can be transferred to the substrate.