Viscous-gravity spreading of time-varying liquid drop volumes on solid surfaces

Chebbi, Rachid

doi:10.1016/j.jcis.2006.04.018

Cited by 8 publications

(3 citation statements)

References 19 publications

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“…After the fingers had disappeared, the meniscus surface appeared to be smooth, but it continued to grow as a circular featureless neck (Figures c and f), as previously reported by others. ,− …”

Section: Resultssupporting

confidence: 81%

Transient Interfacial Patterns and Instabilities Associated with Liquid Film Adhesion and Spreading

et al. 2007

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A surface force apparatus was used to study surface shape changes during the adhesion and spreading of a polymer melt on a bare mica surface. Transient fingers were observed during the initial, rapid spreading process, pointing radially out from the initial adhesive contact point. The fingers had microscopic widths and lengths but submicroscopic thicknesses. They eventually disappeared, leaving a more slowly growing circular neck with a smooth, featureless polymer-air surface. The mean radius of the spreading meniscus (neck) was found to follow a scaling relationship with time of the form (ri + ro)/2 proportional, variant tn, with n = 0.128, while the ends of the fingers grew according to ro proportional, variant tn, with n = 0.10. These rates agree with the values of n = 0.100-0.125 predicted by classical wetting theories for circular macroscopic droplets (i.e., radially symmetric, without fingers) spreading on a solid surface. The lifetime of the transient fingering patterns increases with the polymer viscosity as tau proportional, variant etan, with n = 2.1 +/- 0.2. A circular trough or depression in the film was observed just beyond where the fingers ended, which appears to be a source of the material for the advancing fingers. In addition, beyond the trough, circular ripples/waves were observed on the polymer melt film surface. Such patterns may arise quite generally whenever a perturbation occurs that changes the local forces, thereby inducing a bulge or depression in a liquid film or surface. Thus, we observe similar fingers and ripples/waves during the spreading of liquid polybutadiene on (the immiscible and more viscous) liquid poly(dimethylsiloxane), suggesting that the phenomenon may exist in various liquid adhesion and spreading situations. For low viscosity liquids such as water and low molecular weight oils, our scaling relations suggest that the transient patterns will exist for only a few microseconds; this is likely the reason for why they have not yet been observed.

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Section: Resultssupporting

confidence: 81%

Transient Interfacial Patterns and Instabilities Associated with Liquid Film Adhesion and Spreading

et al. 2007

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“…The spreading law of droplets with increasing volume is quite different from the one of spontaneously spreading droplets. 22,23 For example, the radius of a droplet with a linearly increasing volume grows with t 1/2 and the exponent is strongly dependent on the injection rate.…”

Section: Coalescence Dynamics: Some Experimental Resultsmentioning

confidence: 99%

Modeling the coalescence of sessile droplets

Sellier

Trelluyer

2009

Biomicrofluidics

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This paper proposes a simple scenario to describe the coalescence of sessile droplets. This scenario predicts a power-law growth of the bridge between the droplets. The exponent of this power law depends on the driving mechanism for the spreading of each droplet. To validate this simple idea, the coalescence is simulated numerically and a basic experiment is performed. The fluid dynamics problem is formulated in the lubrication approximation framework and the governing equations are solved in the commercial finite element software COMSOL. Although a direct comparison of the numerical results with experiment is difficult because of the sensitivity of the coalescence to the initial and operating conditions, the key features of the event are qualitatively captured by the simulation and the characteristic time scale of the dynamics recovered. The experiment consists of inducing coalescence by pumping a droplet through a substrate which grows and ultimately coalesces with another droplet resting on the substrate. The coalescence was recorded using high-speed imaging and also confirmed the power-law growth of the neck.

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“…Physical mechanisms of wetting can be described by molecular-kinetic theory or hydrodynamics. Accordingly, wetting is considered either in terms of the kinetics of molecular processes occurring in a contact line [4][5][6][7] or the effect of the viscous stress on a contact angle change (dynamic contact angle change) while spreading [8,9].…”

Section: Introductionmentioning

confidence: 99%

Change of Dynamic Contact Angle of a Drop Spreading over Copper Surface

Feoktistov

Orlova

Islamova

2015

MATEC Web of Conferences

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Abstract. This work presents the comparison between the change of a dynamic contact angle during drop spreading over copper surfaces obtained in the experiment and calculated by using empirical correlations (Bracke et al., Jiang et al., Seebergh et al.). It is found that these correlations are applicable for the case of drop spreading over a smooth surface or over a rough surface into the low capillary number region (2.5·10 -7 ). Dynamic contact angles obtained experimentally increase with increasing capillary number, besides it increases significantly on more rough surfaces. However the calculated values of angles do not depend on Ca.

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Viscous-gravity spreading of time-varying liquid drop volumes on solid surfaces

Cited by 8 publications

References 19 publications

Transient Interfacial Patterns and Instabilities Associated with Liquid Film Adhesion and Spreading

Transient Interfacial Patterns and Instabilities Associated with Liquid Film Adhesion and Spreading

Modeling the coalescence of sessile droplets

Change of Dynamic Contact Angle of a Drop Spreading over Copper Surface

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