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Dissipation in rapid dynamic wetting
KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.ORCID iD: 0000-0003-2830-0454
KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.ORCID iD: 0000-0003-3336-1462
2011 (English)In: Journal of Fluid Mechanics, ISSN 0022-1120, E-ISSN 1469-7645, Vol. 682, 213-240 p.Article in journal (Refereed) Published
Abstract [en]

In this article, we present a modelling approach for rapid dynamic wetting based on the phase field theory. We show that in order to model this accurately, it is important to allow for a non-equilibrium wetting boundary condition. Using a condition of this type, we obtain a direct match with experimental results reported in the literature for rapid spreading of liquid droplets on dry surfaces. By extracting the dissipation of energy and the rate of change of kinetic energy in the flow simulation, we identify a new wetting regime during the rapid phase of spreading. This is characterized by the main dissipation to be due to a re-organization of molecules at the contact line, in a diffusive or active process. This regime serves as an addition to the other wetting regimes that have previously been reported in the literature.

Place, publisher, year, edition, pages
2011. Vol. 682, 213-240 p.
Keyword [en]
contact lines, drops, interfacial flows (free surface)
National Category
Physical Sciences
URN: urn:nbn:se:kth:diva-41294DOI: 10.1017/jfm.2011.211ISI: 000294775800010ScopusID: 2-s2.0-80052182393OAI: diva2:444305
Swedish Research Council
QC 20110928Available from: 2011-09-28 Created: 2011-09-26 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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