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Modeling of dynamic wetting far from equilibrium
KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.ORCID iD: 0000-0003-2830-0454
KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.ORCID iD: 0000-0003-3336-1462
2009 (English)In: Physics of fluids, ISSN 1070-6631, E-ISSN 1089-7666, Vol. 21, no 12Article in journal (Refereed) Published
Abstract [en]

In this paper we present simulations of dynamic wetting far from equilibrium based on phase field theory. In direct simulations of recent experiments [J. C. Bird, S. Mandre, and H. A. Stone, Phys. Rev. Lett. 100, 234501 (2008)], we show that in order to correctly capture the dynamics of rapid wetting, it is crucial to account for nonequilibrium at the contact line, where the gas, liquid, and solid meet. A term in the boundary condition at the solid surface that naturally arises in the phase field theory is interpreted as allowing for the establishment of a local structure in the immediate vicinity of the contact line. A direct qualitative and quantitative match with experimental data of spontaneously wetting liquid droplets is shown.

Place, publisher, year, edition, pages
2009. Vol. 21, no 12
Keyword [en]
drops, flow simulation, wetting, contact-line, interface
URN: urn:nbn:se:kth:diva-19088DOI: 10.1063/1.3275853ISI: 000273216700001ScopusID: 2-s2.0-76249091583OAI: diva2:337135
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2012-03-13Bibliographically approved
In thesis
1. Capillarity and dynamic wetting
Open this publication in new window or tab >>Capillarity and dynamic wetting
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis capillary dominated two–phase flow is studied by means of nu- merical simulations and experiments. The theoretical basis for the simulations consists of a phase field model, which is derived from the system’s thermody- namics, and coupled with the Navier Stokes equations. Two types of interfacial flow are investigated, droplet dynamics in a bifurcating channel and sponta- neous capillary driven spreading of drops.

Microfluidic and biomedical applications often rely on a precise control of droplets as they traverse through complicated networks of bifurcating channels. Three–dimensional simulations of droplet dynamics in a bifurcating channel are performed for a set of parameters, to describe their influence on the resulting droplet dynamics. Two distinct flow regimes are identified as the droplet in- teracts with the tip of the channel junction, namely, droplet splitting and non- splitting. A flow map based on droplet size and Capillary number is proposed to predict whether the droplet splits or not in such a geometry.

A commonly occurring flow is the dynamic wetting of a dry solid substrate. Both experiments and numerical simulations of the spreading of a drop are presented here. A direct comparison of the two identifies a new parameter in the phase field model that is required to accurately predict the experimental spreading behavior. This parameter μf [P a · s], is interpreted as a friction factor at the moving contact line. Comparison of simulations and experiments for different liquids and surface wetting properties enabled a measurement of the contact line friction factor for a wide parameter space. Values for the contact line friction factor from phase field theory are reported here for the first time.

To identify the physical mechanism that governs the droplet spreading, the different contributions to the flow are measured from the simulations. An im- portant part of the dissipation may arise from a friction related to the motion of the contact line itself, and this is found to be dominating both inertia and viscous friction adjacent to the contact line. A scaling law based on the con- tact line friction factor collapses the experimental data, whereas a conventional inertial or viscous scaling fails to rationalize the experimental observation, supporting the numerical finding.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. xi, 50 p.
Trita-MEK, ISSN 0348-467X ; 2012:01
National Category
Fluid Mechanics and Acoustics Computational Mathematics
urn:nbn:se:kth:diva-91329 (URN)978-91-7501-282-7 (ISBN)
Public defence
2012-03-23, Salongen KTHB, Osquars Backe 25, KTH, Stockholm, 10:00 (English)
Swedish e‐Science Research Center

QC 20120313

Available from: 2012-03-13 Created: 2012-03-13 Last updated: 2013-04-09Bibliographically approved

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Carlson, AndreasDo-Quang, MinhAmberg, Gustav
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