Physics of Fluids - Publications

Absorption of surfactant-laden droplets into porous media: A numerical study

Journal of Colloid and Interface Science 597, 149–159 (2021)

Authors

	R.T. van Gaalen
	Christian Diddens
	D.P. Siregar
	Herman Wijshoff
	J.G.M. Kuerten

BibTeΧ

@article{VANGAALEN2021149,
title = {Absorption of surfactant-laden droplets into porous media: A numerical study},
journal = {Journal of Colloid and Interface Science},
volume = {597},
pages = {149-159},
year = {2021},
issn = {0021-9797},
doi = {https://doi.org/10.1016/j.jcis.2021.03.119},
url = {https://www.sciencedirect.com/science/article/pii/S0021979721004197},
author = {R.T. {van Gaalen} and C. Diddens and D.P. Siregar and H.M.A. Wijshoff and J.G.M. Kuerten},
keywords = {Droplets, Soluble surfactants, Absorption, Lubrication approximation, Porous media, Darcy's law},
abstract = {Hypothesis
Droplets can absorb into permeable substrates due to capillarity. It is hypothesized that the contact line dynamics influence this process and that an unpinned contact line results in slower absorption than a pinned contact line, since the contact area between the droplet and the substrate will decrease over time for the former. Furthermore, it is expected that surfactants can be used to accelerate the absorption.
Simulations
Lubrication theory is employed to model the droplet and Darcy‚Äôs law is combined with the conservation law of mass to describe the absorption dynamics. For the surfactant transport, several convection-diffusion-adsorption equations are solved.
Findings
It is found that moving contact lines result in a parabola-shaped wetted area and a slower absorption and a deeper penetration depth than pinned contact lines. The evolution of the penetration depth was quantitatively validated by comparison with two experimental studies from literature. Surfactants were shown to accelerate the absorption process, but only if their adsorption kinetics are slow compared to the absorption. Otherwise, all surfactant adsorbs onto the pore walls before reaching the wetting front, resulting in the same absorption rate as without surfactants. This behavior agrees with both experimental and analytical literature.}
}