INTEC   05402
INSTITUTO DE DESARROLLO TECNOLOGICO PARA LA INDUSTRIA QUIMICA
Unidad Ejecutora - UE
artículos
Título:
Liquid film drag out in the presence of molecular forces
Autor/es:
SCHMIDHALTER, I.; CERRO, R. L.; GIAVEDONI, M. D.; SAITA, F. A.
Revista:
PHYSICS OF FLUIDS
Editorial:
AMER INST PHYSICS
Referencias:
Lugar: New York; Año: 2013 vol. 25 p. 1 - 13
ISSN:
1070-6631
Resumen:
From a practical as well as a conceptual point of view, one of the most interesting
problems of physicochemical hydrodynamics is the drag out of a liquid film by
a moving solid out of a pool of liquid. The basic problem, sometimes denoted the
Landau-Levich problem [L. Landau and B. Levich, ?Dragging of a liquid by amoving
plate,? Acta Physicochim. USSR 17, 42?54 (1942)], involves an interesting blend of
capillary and viscous forces plus a matching of the static solution for capillary rise
with a numerical solution of the film evolution equation, neglecting gravity, on the
downstream region of the flow field. The original solution describes experimental
data for a wide range of Capillary numbers but fails to match results for large and
very small Capillary numbers. Molecular level forces are introduced to create an
augmented version of the film evolution equation to show the effect of van derWaals
forces at the lower range of Capillary numbers. A closed form solution for static
capillary rise, including molecular forces, was matched with a numerical solution of
the augmented film evolution equation in the dynamic meniscus region. Molecular
forces do not sensibly modify the static capillary rise region, since film thicknesses
are larger than the range of influence of van der Waals forces, but are determinant in
shaping the downstream dynamic meniscus of the very thin liquid films. As expected,
a quantitatively different level of disjoining pressure for different values of molecular
constants remains in the very thin liquid film far downstream. Computational results
for a wide range of Capillary numbers and Hamaker constants show a clear transition
towards a region where the film thickness becomes independent of the coating speed.