Partial coalescence of a drop on a larger-viscosity pool

Abstract
When a low-viscosity drop coalesces with a pool surface of the same liquid, it often portrays partial coalescence, where it pinches off a daughter droplet from its top. Such partial coalescence can also occur for a drop spreading on a strongly hydrophilic solid surface. Herein, we investigate the partial coalescence of a low-viscosity drop with a pool surface, when the viscosity of the miscible pool is changed from low to very high, in other words, spanning the conditions from a pool to a solid surface. We find that above a certain pool viscosity, the partial coalescence transitions to second-stage coalescence with a much smaller satellite droplet. This occurs because higher pool viscosity prevents drainage from the drop into the pool, which, in turn, increases the axial curvature in the neck connecting the primary satellite to the drop, thereby preventing the first-stage pinch-off.

Citation
Alhareth, A. A., & Thoroddsen, S. T. (2020). Partial coalescence of a drop on a larger-viscosity pool. Physics of Fluids, 32(12), 122115. doi:10.1063/5.0035019

Acknowledgements
This research was funded by the King Abdullah University of Science and Technology (KAUST) under Grant No. URF/1/3727-01-01. A.A.A.’s Ph.D. study was supported by the Center of Excellence for Aeronautics and Astronautics (CEAA) at King Abdulaziz City for Science and Technology (KACST).

Publisher
AIP Publishing

Journal
Physics of Fluids

DOI
10.1063/5.0035019

Additional Links
http://aip.scitation.org/doi/10.1063/5.0035019

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