Contact line motion in confined liquid–gas systems: Slip versus phase transition

Handle URI:
http://hdl.handle.net/10754/552762
Title:
Contact line motion in confined liquid–gas systems: Slip versus phase transition
Authors:
Xu, Xinpeng; Qian, Tiezheng
Abstract:
In two-phase flows, the interface intervening between the two fluid phases intersects the solid wall at the contact line. A classical problem in continuum fluid mechanics is the incompatibility between the moving contact line and the no-slip boundary condition, as the latter leads to a nonintegrable stress singularity. Recently, various diffuse-interface models have been proposed to explain the contact line motion using mechanisms missing from the sharp-interface treatments in fluid mechanics. In one-component two-phase (liquid–gas) systems, the contact line can move through the mass transport across the interface while in two-component (binary) fluids, the contact line can move through diffusive transport across the interface. While these mechanisms alone suffice to remove the stress singularity, the role of fluid slip at solid surface needs to be taken into account as well. In this paper, we apply the diffuse-interface modeling to the study of contact line motion in one-component liquid–gas systems, with the fluid slip fully taken into account. The dynamic van der Waals theory has been presented for one-component fluids, capable of describing the two-phase hydrodynamics involving the liquid–gas transition [A. Onuki, Phys. Rev. E 75, 036304 (2007)]. This theory assumes the local equilibrium condition at the solid surface for density and also the no-slip boundary condition for velocity. We use its hydrodynamicequations to describe the continuum hydrodynamics in the bulk region and derive the more general boundary conditions by introducing additional dissipative processes at the fluid–solid interface. The positive definiteness of entropy production rate is the guiding principle of our derivation. Numerical simulations based on a finite-difference algorithm have been carried out to investigate the dynamic effects of the newly derived boundary conditions, showing that the contact line can move through both phase transition and slip, with their relative contributions determined by a competition between the two coexisting mechanisms in terms of entropy production. At temperatures very close to the critical temperature, the phase transition is the dominant mechanism, for the liquid–gas interface is wide and the density ratio is close to 1. At low temperatures, the slip effect shows up as the slip length is gradually increased. The observed competition can be interpreted by the Onsager principle of minimum entropy production
Citation:
Contact line motion in confined liquid–gas systems: Slip versus phase transition 2010, 133 (20):204704 The Journal of Chemical Physics
Publisher:
AIP Publishing
Journal:
The Journal of Chemical Physics
Issue Date:
30-Nov-2010
DOI:
10.1063/1.3506886
Type:
Article
ISSN:
00219606
Additional Links:
http://scitation.aip.org/content/aip/journal/jcp/133/20/10.1063/1.3506886
Appears in Collections:
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Full metadata record

DC FieldValue Language
dc.contributor.authorXu, Xinpengen
dc.contributor.authorQian, Tiezhengen
dc.date.accessioned2015-05-14T06:32:35Zen
dc.date.available2015-05-14T06:32:35Zen
dc.date.issued2010-11-30en
dc.identifier.citationContact line motion in confined liquid–gas systems: Slip versus phase transition 2010, 133 (20):204704 The Journal of Chemical Physicsen
dc.identifier.issn00219606en
dc.identifier.doi10.1063/1.3506886en
dc.identifier.urihttp://hdl.handle.net/10754/552762en
dc.description.abstractIn two-phase flows, the interface intervening between the two fluid phases intersects the solid wall at the contact line. A classical problem in continuum fluid mechanics is the incompatibility between the moving contact line and the no-slip boundary condition, as the latter leads to a nonintegrable stress singularity. Recently, various diffuse-interface models have been proposed to explain the contact line motion using mechanisms missing from the sharp-interface treatments in fluid mechanics. In one-component two-phase (liquid–gas) systems, the contact line can move through the mass transport across the interface while in two-component (binary) fluids, the contact line can move through diffusive transport across the interface. While these mechanisms alone suffice to remove the stress singularity, the role of fluid slip at solid surface needs to be taken into account as well. In this paper, we apply the diffuse-interface modeling to the study of contact line motion in one-component liquid–gas systems, with the fluid slip fully taken into account. The dynamic van der Waals theory has been presented for one-component fluids, capable of describing the two-phase hydrodynamics involving the liquid–gas transition [A. Onuki, Phys. Rev. E 75, 036304 (2007)]. This theory assumes the local equilibrium condition at the solid surface for density and also the no-slip boundary condition for velocity. We use its hydrodynamicequations to describe the continuum hydrodynamics in the bulk region and derive the more general boundary conditions by introducing additional dissipative processes at the fluid–solid interface. The positive definiteness of entropy production rate is the guiding principle of our derivation. Numerical simulations based on a finite-difference algorithm have been carried out to investigate the dynamic effects of the newly derived boundary conditions, showing that the contact line can move through both phase transition and slip, with their relative contributions determined by a competition between the two coexisting mechanisms in terms of entropy production. At temperatures very close to the critical temperature, the phase transition is the dominant mechanism, for the liquid–gas interface is wide and the density ratio is close to 1. At low temperatures, the slip effect shows up as the slip length is gradually increased. The observed competition can be interpreted by the Onsager principle of minimum entropy productionen
dc.publisherAIP Publishingen
dc.relation.urlhttp://scitation.aip.org/content/aip/journal/jcp/133/20/10.1063/1.3506886en
dc.rightsArchived with thanks to The Journal of Chemical Physicsen
dc.titleContact line motion in confined liquid–gas systems: Slip versus phase transitionen
dc.typeArticleen
dc.identifier.journalThe Journal of Chemical Physicsen
dc.eprint.versionPublisher's Version/PDFen
dc.contributor.institutionNano Science and Technology (NSNT) Program, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kongen
dc.contributor.institutionDepartment of Mathematics, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kongen
kaust.authorQian, Tiezhengen
kaust.grant.fundedcenterKAUST-HKUST Micro/Nanofluidic Joint Laboratoryen
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