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Hydrodynamic density-functional theory for the moving contact-line problem reveals fluid structure and emergence of a spatially distinct pattern

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posted on 2025-05-06, 13:29 authored by Andreas Nold, Benjamin Goddard, David SibleyDavid Sibley, Serafim Kalliadasis

Understanding the nanoscale effects controlling the dynamics of a contact line—defined as the line formed at the junction of two fluid phases and a solid—has been a longstanding problem in fluid mechanics pushing experimental and numerical methods to their limits. A major challenge is the multiscale nature of the problem, whereby nanoscale phenomena manifest themselves at the macroscale. To probe the nanoscale, not easily accessible to other methods, we propose a reductionist model that employs elements from statistical mechanics, namely, dynamic-density-functional theory (DDFT), in a Navier-Stokes-like equation—an approach we name hydrodynamic DDFT. The model is applied to an isothermal Lennard-Jones fluid with no slip on a flat solid substrate. Our computations reveal fluid stratification with an oscillatory density structure close to the wall and the emergence of two distinct regions as the temperature increases: a region of compression on the vapor side of the liquid-vapor interface and an effective slip region of large shear on the liquid side. The compressive region spreads along the fluid interface at a lengthscale that increases faster than the width of the fluid interface with temperature, while the width of the slip region is bound by the oscillatory fluid density structure and is constrained to a few particle diameters from the wall. Both compressive and shear effects may offset contact line friction, while compression in particular has a disproportionately high effect on the speed of advancing contact lines at low temperatures.

Funding

Machine-Aided General Framework for Fluctuating Dynamic Density Functional Theory (MAGFFDDFT)

UK Research and Innovation

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European Research Council via Advanced Grant No. 247031

Multiscale Analysis of Complex Interfacial Phenomena (MACIPh): Coarse graining, Molecular modelling, stochasticity, and experimentation

Engineering and Physical Sciences Research Council

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DTG International Studentship

Joachim Herz Foundation through an “Add-on Fellowships for Interdisciplinary Science”

History

School

  • Science

Published in

Physical Review Fluids

Volume

9

Issue

12

Publisher

American Physical Society

Version

  • VoR (Version of Record)

Rights holder

© The Author(s)

Publisher statement

Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

Acceptance date

2024-10-01

Publication date

2024-12-09

Copyright date

2024

ISSN

2469-990X

eISSN

2469-990X

Language

  • en

Depositor

Dr David Sibley. Deposit date: 9 December 2024

Article number

124003