Coalescence of sessile drops
We present an experimental and theoretical description of the kinetics of coalescence of two water drops on a plane solid surface. The case of partial wetting is considered. The drops are in an atmosphere of nitrogen saturated with water where they grow by condensation and eventually touch each othe...
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Published in | Journal of fluid mechanics Vol. 453; pp. 427 - 438 |
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Main Authors | , , , |
Format | Journal Article |
Language | English |
Published |
Cambridge, UK
Cambridge University Press
25.02.2002
Cambridge University Press (CUP) |
Subjects | |
Online Access | Get full text |
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Summary: | We present an experimental and theoretical description of the kinetics of coalescence
of two water drops on a plane solid surface. The case of partial wetting is considered.
The drops are in an atmosphere of nitrogen saturated with water where they grow by
condensation and eventually touch each other and coalesce. A new convex composite
drop is rapidly formed that then exponentially and slowly relaxes to an equilibrium
hemispherical cap. The characteristic relaxation time is proportional to the drop
radius R* at final equilibrium. This relaxation time appears to be nearly 107 times
larger than the bulk capillary relaxation time tb = R*η/σ, where σ is the gas–liquid
surface tension and η is the liquid shear viscosity. In order to explain this extremely large relaxation time, we consider a model that
involves an Arrhenius kinetic factor resulting from a liquid–vapour phase change in
the vicinity of the contact line. The model results in a large relaxation time of order
tb exp(L/[Rscr ]T) where L is the molar latent heat of vaporization, [Rscr ] is the gas constant
and T is the temperature. We model the late time relaxation for a near spherical cap
and find an exponential relaxation whose typical time scale agrees reasonably well
with the experiment. |
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Bibliography: | ark:/67375/6GQ-RC46BJBD-P istex:6AB62D4BB4FE366C2E2B1AA8EEC8AE8BE0C445E7 PII:S0022112001007121 ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 23 |
ISSN: | 0022-1120 1469-7645 |
DOI: | 10.1017/S0022112001007121 |