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Contact line dynamics in drop coalescence and spreading
R Narhe1, D Beysens, V S Nikolayev
1Equipe du Supercritique pour l'Environnement, les Matériaux et l'Espace, Service des Basses Températures, CEA-Grenoble, Grenoble, France.
Langmuir : the ACS Journal of Surfaces and Colloids
|April 5, 2005
Summary
The study reveals that water drop coalescence dynamics are significantly slower than predicted due to contact line dissipation. Drop oscillations, induced by syringe deposition, accelerate coalescence compared to condensation methods.
Area of Science:
- Fluid Dynamics
- Surface Science
- Wettability Studies
Background:
- Investigating the dynamics of sessile water drop coalescence.
- Comparing coalescence with single drop spreading in partially wetting conditions.
Purpose of the Study:
- To analyze the relaxation dynamics of composite drops formed by coalescence.
- To determine factors influencing relaxation time, including contact angle, drop size, and surface properties.
Main Methods:
- Observing water drop coalescence and single drop spreading.
- Utilizing syringe deposition and condensation chamber methods for initiating coalescence.
- Employing high-speed camera filming to capture dynamics.
Main Results:
- Coalescence relaxation time exhibits exponential decay with contact angle, influenced by drop size and surface properties.
- Observed relaxation dynamics are 5-6 orders of magnitude slower than bulk hydrodynamics predictions due to contact line dissipation.
- Syringe deposition leads to an order of magnitude faster dynamics than condensation due to induced drop oscillations.
Conclusions:
- High dissipation in the contact line vicinity significantly slows down coalescence dynamics.
- Drop oscillations, excited by syringe deposition, enhance contact line motion and accelerate coalescence.
- Understanding these dynamics is crucial for applications involving fluid interfaces and surface interactions.