Steady moving contact line of water over a no-slip substrate

Abstract

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 can 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.

arXiv comment26 pages, 13 figures, 4 tables, post-review version, under consideration for publication in "European Physical Journal Special Topics"

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• Implementing contact angle boundary conditions for second-order Phase-Field models of wall-bounded multiphase flows
• Droplet motion on chemically heterogeneous substrates with mass transfer. II. Three-dimensional dynamics
• Asymmetry of wetting and de-wetting on high-friction surfaces originates from the same molecular physics
• Mass diffusion and bending in dynamic wetting by phase-field and sharp-interface models