Hydrodynamic density-functional theory for the moving contact-line problem reveals fluid structure and emergence of a spatially distinct pattern
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
Find out more...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
Find out more...DTG International Studentship
Joachim Herz Foundation through an “Add-on Fellowships for Interdisciplinary Science”
History
School
- Science
Published in
Physical Review FluidsVolume
9Issue
12Publisher
American Physical SocietyVersion
- VoR (Version of Record)
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© 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
2024-10-01Publication date
2024-12-09Copyright date
2024ISSN
2469-990XeISSN
2469-990XPublisher version
Language
- en