On Spread Extent of Sessile Droplet into Porous Medium: Numerical Solution and Comparisons with Experiments

Document Type

Article

Publication Date

1-8-2010

Publication Title

Physics of Fluids

Abstract

The spread of a wetting liquid sessile droplet into porous medium is solved numerically using the capillary network model with a microforce balance boundary condition at the liquid/gas free interface in the porous medium. The spread starts as the porous medium imbibes the sessile liquid, followed by liquid additionally being spread inside the porous medium itself. After there is no remaining sessile liquid, the net flow across the porous medium boundaries is equal to zero. Either spread, with or without sessile liquid present at the porous medium surface, is rendered by local differences in capillary pressure. These local differences are accounted for by implementing the numerical solution over a heterogeneous capillary network, consisting of pores connected by throats. Both pores and throats follow predefined distribution functions. Once there is no sessile liquid present on the porous medium surface, it is found from a numerical solution that the liquid front can extend significantly in time, wetting very large volumes of the porous medium. This is also measured in experiments, in which over time, an increase in wetted volume of more than 16 times is observed compared to the wetted volume right after the disappearance of sessile liquid on the porous medium surface. The numerical and experimental results for the time changes of (i) volume of liquid remaining at the porous medium surface, (ii) porous medium surface wetted area of the droplet imprint, and (iii) liquid protrusion depth into porous medium are compared, with very good qualitative and quantitative agreement found.

Volume

22

Issue

1

DOI

https://doi.org/10.1063/1.3284782

ISSN

1070-6631

Comments

ESSN: 1089-7666

Rights

© 2010 AIP Publishing

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