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Symmetric drop coalescence on an under-liquid substrate
Surjyasish Mitra1, Sushanta K Mitra1
1Micro and Nano-scale Transport Laboratory, Department of Mechanical Engineering, Lassonde School of Engineering, York University, Toronto, Ontario, Canada M3J 1P3.
Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics
|October 15, 2015
Summary
This study reveals a new time scale governing droplet coalescence under liquid. Droplet bridge growth transitions from universal scaling to slower growth, differing from air coalescence.
Area of Science:
- Fluid dynamics
- Surface science
- Colloid science
Background:
- Coalescence of sessile drops is crucial in various industrial and natural processes.
- Understanding drop coalescence under liquid substrates presents unique challenges compared to air.
Purpose of the Study:
- To investigate the early coalescence behavior of symmetric sessile drops under liquid substrates.
- To develop a modified lubrication equation accounting for fluid viscosities.
Main Methods:
- Derivation of a modified one-dimensional lubrication equation.
- Analysis of bridge height growth and profile evolution during coalescence.
Main Results:
- Identification of a characteristic time scale governing the coalescence process.
- Discovery of a crossover time separating universal bridge height growth (h*~t*) from slower growth (h*~t*^0.24).
- Observed self-similar bridge profiles that break down earlier for under-liquid coalescence than in air.
Conclusions:
- The derived model accurately describes early under-liquid drop coalescence.
- Viscosity effects significantly influence the dynamics and scaling laws of drop coalescence.
- Under-liquid coalescence exhibits distinct self-similarity breakdown compared to air coalescence.
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