Coalescence of sessile drops
TLDR
Nikolayev et al. as mentioned in this paper presented an experimental and theoretical description of the kinetics of coalescence of two sessile water drops on a plane solid surface, where the drops are in an atmosphere of nitrogen saturated with water where they grow by condensation and eventually touch each other and coalesce.Abstract:
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 10 7 times larger than the bulk capillary relaxation time t b = R * $\eta$/$\sigma$, where $\sigma$ is the gas--liquid surface tension and $\eta$ 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 t b exp(L/RT) where L is the molar latent heat of vaporization, R 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 1 Introduction Fusion or coalescence between drops is a key process in a wide range of phenomena: phase transition in fluids and liquid mixtures or polymers, stability of foams and emulsions, and sintering in metallurgy (Eggers 1998), which is why the problem of coalescence has already received considerable attention Most of the studies of this process so far have been devoted to the coalescence of two spherical drops floating in a medium The kinetics of the process before and after the drops have touched each other is governed by the hydrodynamics inside and outside the drops and by the van der Waals forces when the drops are within mesoscopic distance from each other (Yiantsios \& Davis 1991) The composite drop that results from the coalescence of two drops relaxes to a spherical shape within a time which is dominated by the relaxation of the flow inside and outside (Nikolayev, Beysens \& Guenoun 1996; Nikolayev \& Beysens 1997) There are no studies, to our knowledge, of the coalescence of two sessile drops after they touch each other In this paper, we report a preliminary study of the dynamics and morphology of this process, in the case of hemispherical water droplets which grow slowly on a plane surface at the expense of the surrounding atmosphere, forming what is called 'dew' or 'breath figures' (Beysens et al 1991; Beysens 1995) The drops eventually touch each other and coalesce to form an elongated compositeread more
Citations
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Dew nucleation and growth
Daniel Beysens,Daniel Beysens +1 more
TL;DR: Beysens et al. as mentioned in this paper showed that the drop interaction through drop fusion or coalescence leads to scaling in the growth of droplets and gives universality to the process.
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Numerical simulations of self-propelled jumping upon drop coalescence on non-wetting surfaces
TL;DR: In this article, three-dimensional phase-field simulations of two identical spherical drops coalescing on a flat surface with a contact angle of 180° were performed to investigate the mechanism of self-propelled jumping.
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The structure and stability of multiple micro-droplets
TL;DR: In this paper, the authors explore and control new morphologies of multiple Janus droplets, i.e., arbitrarily long chains of alternating immiscible segments, and explore the vistas to control the morphology of Janus swarms.
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Nature's moisture harvesters: a comparative review
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References
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Wetting: Statics and dynamics
TL;DR: In this article, experimental studies of wetting phenomena have helped to bridge the gap between the progress made in theory and simulation over the past decade, and the experimental evidence or verification of the theoretical predictions.
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Moving contact lines in the Cahn-Hilliard theory
TL;DR: In this article, the equations of motion of an isothermal viscous Cahn-Hilliard fluid were established and the dynamics of fluids having moving contact lines under this theory was investigated, showing that the force singularity arising in the classical model of capillarity is no longer present.
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The formation of dew
TL;DR: In this article, the authors review the aspects related to heterogeneous nucleation and subsequent growth of water droplets on a substrate and consider the effects of substrate heterogeneity and gravity effects.
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The spreading of volatile liquid droplets on heated surfaces
TL;DR: In this paper, a two-dimensional volatile liquid droplet on a uniformly heated horizontal surface is considered and a new contact line condition based on mass balance is formulated and used, which represents a leading-order superposition of spreading and evaporative effects.
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Close approach and deformation of two viscous drops due to gravity and van der waals forces
S.G. Yiantsios,Robert H. Davis +1 more
TL;DR: In this article, the rate of approach and deformation of two small drops of different sizes in buoyancy-driven axi-symmetric motion is analyzed within the asymptotic limit of small capillary number, in which deformation becomes important only when the minimum separation between the drops is much smaller than either radius.