Dong, T;
Weheliye, WH;
Angeli, P;
(2019)
Laser induced fluorescence studies on the distribution of surfactants during drop/interface coalescence.
Physics of Fluids
, 31
, Article 012106. 10.1063/1.5059554.
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Abstract
The spatiotemporal distribution of fluorescent surfactants on the merging interfaces during the coalescence of an aqueous drop with an organic/aqueous flat interface was studied experimentally with high-speed laser induced fluorescence. The aqueous phase was a 46% glycerol solution, while the organic phase was a 5 cSt silicone oil. A fluorescently tagged surfactant was used at a concentration of 0.001 mol/m3 in the aqueous phase. To vary the concentration of surfactants on the interfaces, the drop and the flat interface were left to stand for different times before the coalescence experiments (different interface ages). It was found that when a drop rested on the interface, the surfactants adsorbed on the interfaces were swept outwards by the draining liquid film between the drop and the flat interface and reached a peak value at 0.75Rh away from the centre of the film, where Rh is the horizontal drop radius. After the film rupture, the concentration of the surfactants at the tip of the meniscus increased. Once the film had retracted, the concentration of the surfactants peaked at the meniscus at the bottom of the drop. As the liquid in the drop started to merge with its homophase, the drop formed a cylinder from the upward capillary waves on the drop surface. The surfactant concentration was found to be low at the top of the liquid cylinder as the interface was stretched by the convergence of the capillary waves. Subsequently, the cylinder began to shrink and the top part of the drop acquired a high surfactant concentration.
| Type: | Article |
|---|---|
| Title: | Laser induced fluorescence studies on the distribution of surfactants during drop/interface coalescence |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1063/1.5059554 |
| Publisher version: | http://doi.org/10.1063/1.5059554 |
| Language: | English |
| Additional information: | Copyright © 2019 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/). https://doi.org/10.1063/1.5059554 |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Chemical Engineering UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Med Phys and Biomedical Eng |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10068585 |
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