Forced Wetting Dynamics:  A Molecular Dynamics Study

Gentner, Fabien; Ogonowski, G.; Coninck, J. De

doi:10.1021/la020724j

Cited by 25 publications

(19 citation statements)

References 19 publications

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“…(19), are seen to agree within 10%, which is comparable to the discrepancy of up to 20% observed in Thompson et al 14 . This is attributed by Thompson et al 14 to residual stresses in the solid and the microscale invalidity of Young's relation 53 .…”

Section: A1 Wall Fluid Interaction and Equilbirum Anglesupporting

confidence: 85%

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A Langevin model for fluctuating contact angle behaviour parametrised using molecular dynamics

2016

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Molecular dynamics simulations are employed to develop a theoretical model to predict the fluidsolid contact angle as a function of wall-sliding speed incorporating thermal fluctuations. A liquid bridge between counter-sliding walls is studied, with liquid-vapour interface-tracking, to explore the impact of wall-sliding speed on contact angle. The behaviour of the macroscopic contact angle varies linearly over a range of capillary numbers beyond which the liquid bridge pinches off, a behaviour supported by experimental results. Nonetheless, the liquid bridge provides an ideal test case to study molecular scale thermal fluctuations, which are shown to be well described by Gaussian distributions. A Langevin model for contact angle is parametrised to incorporate the mean, fluctuation and auto-correlations over a range of sliding speeds and temperatures. The resulting equations can be used as a proxy for the fully-detailed molecular dynamics simulation allowing them to be integrated within a continuum-scale solver.

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Section: A1 Wall Fluid Interaction and Equilbirum Anglesupporting

confidence: 85%

“…In the literature, the non-linear behaviour of Cox's law 13,14 and the cubic dependence of Tanner's law 19 have been observed in a similar molecular geometry. The agreement of molecular scale simulation to macroscopic laws for droplet motions is somewhat surprising.…”

Section: Mean Contact Anglementioning

confidence: 88%

A Langevin model for fluctuating contact angle behaviour parametrised using molecular dynamics

2016

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“…Over recent decades MD has become an important complement to macroscopic modelling (Koplik, Banavar & Willemsen 1988;Thompson & Robbins 1989;Gentner, Ogonowski & De Coninck 2003;Qian, Wang & Sheng 2004), particularly since it allows modelling of the nanoscopic physics at the contact line. Studies of wetting using MD have mostly been limited by the available computational power, with system sizes a few times larger than the typical interaction range between molecules of ≈1 nm (Liu, Qin & Yang 2010;Ho et al 2011;Ritos et al 2013), which may lead to finite-size effects in the results.…”

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confidence: 99%

Water–substrate physico-chemistry in wetting dynamics

2015

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We consider the wetting of water droplets on substrates with different chemical composition and molecular spacing, but with an identical equilibrium contact angle. A combined approach of large-scale molecular dynamics simulations and a continuum phase field model allows us to identify and quantify the influence of the microscopic physics at the contact line on the macroscopic droplet dynamics. We show that the substrate physico-chemistry, in particular hydrogen bonding, can significantly alter the flow. Since the material parameters are systematically derived from the atomistic simulations, our continuum model has only one adjustable parameter, which appears as a friction factor at the contact line. The continuum model approaches the atomistic wetting rate only when we adjust this contact line friction factor. However, the flow appears to be qualitatively different when comparing the atomistic and continuum models, highlighting that non-trivial continuum effects can come into play near the interface of the wetting front.

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“…Alternatively, to clarify the phenomena near the moving contact line, non-continuum models are used. For instance, molecular dynamics (MD) simulations (Gentner, Ogonowski & De Coninck 2003;Blake 2006) and lattice-Boltzmann (LB) simulations (Blake, De Coninck & d'Ortona 1995;Mo, Liu & Kwok 2005) are used to study mechanism of contact line dynamics. These simulations are well suited to study microscopic systems (Bonn et al 2009).…”

Section: Introductionmentioning

confidence: 99%

Experimental and theoretical study of dewetting corner flow

et al. 2014

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We study a partial dewetting corner flow with a moving contact line at a finite Reynolds number, 0 < Re < O(100). When the speed of the moving contact line increases, the receding contact line appears with a corner shape that is also observed in a gravity-driven liquid droplet on an incline and on a plate withdrawn from a bath. In the current problem, Re is larger than unity, where is the aspect ratio of the flow structure. Therefore, classical lubrication theory is no longer appropriate. We develop a modified three-dimensional lubrication model for the dewetting corner structure at Re > 1 by taking into account the internal flow pattern and by scaling arguments. The key requirement is that the streamlines in the corner are straight and (nearly) parallel. In this case, we can obtain a modified pressure consisting of the capillary pressure and the dynamic pressure. This model describes the three-dimensional dewetting corner structure at the rear of the moving droplets at Re > 1 and furthermore shows that the dynamic pressure effects become dominant at a small half-opening angle. Additionally, this model provides analytical results for the internal flow, which is a self-similar flow pattern. To validate the analytical results, we perform high-speed shadowgraphy and tomographic particle image velocimetry (PIV). We find a good agreement between the theoretical and the experimental results.

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Forced Wetting Dynamics: A Molecular Dynamics Study

Cited by 25 publications

References 19 publications

A Langevin model for fluctuating contact angle behaviour parametrised using molecular dynamics

A Langevin model for fluctuating contact angle behaviour parametrised using molecular dynamics

Water–substrate physico-chemistry in wetting dynamics

Experimental and theoretical study of dewetting corner flow

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