Steady moving contact line of water over a no-slip substrate
Challenges in benchmarking phase-field and volume-of-fluid methods against molecular dynamics simulations
FLOW Centre, Department of Engineering Mechanics KTH,
2 Swedish e-Science Research Centre, Science for Life Laboratory, Department of Applied Physics KTH, 100 44 Stockholm, Sweden
3 Sorbonne Université and CNRS, Paris, France
4 Södertorn University, Stockholm, Sweden
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Accepted: 6 July 2020
Published online: 14 September 2020
The movement of the triple contact line plays a crucial role in many applications such as ink-jet printing, liquid coating and drainage (imbibition) in porous media. To design accurate computational tools for these applications, predictive models of the moving contact line are needed. However, the basic mechanisms responsible for movement of the triple contact line are not well understood but still debated. We investigate the movement of the contact line between water, vapour and a silica-like solid surface under steady conditions in low capillary number regime. We use molecular dynamics (MD) with an atomistic water model to simulate a nanoscopic drop between two moving plates. We include hydrogen bonding between the water molecules and the solid substrate, which leads to a sub-molecular slip length. We benchmark two continuum methods, the Cahn–Hilliard phase-field (PF) model and a volume-of-fluid (VOF) model, against MD results. We show that both continuum models reproduce the statistical measures obtained from MD reasonably well, with a trade-off in accuracy. We demonstrate the importance of the phase-field mobility parameter and the local slip length in accurately modelling the moving contact line.
© The Author(s) 2020
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Open access funding provided by Royal Institute of Technology.