Constante-Amores, CR;
Kahouadji, L;
Shin, S;
Chergui, J;
Juric, D;
Castrejon-Pita, JR;
Matar, OK;
(2023)
Impact of droplets onto surfactant-laden thin liquid films.
Journal of Fluid Mechanics
, 961
, Article A8. 10.1017/jfm.2023.224.
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Abstract
We study the effect of insoluble surfactants on the impact of surfactant-free droplets on surfactant-laden thin liquid films via a fully three-dimensional direct numerical simulations approach that employs a hybrid interface-tracking/level-set method, and by taking into account surfactant-induced Marangoni stresses due to gradients in interfacial surfactant concentration. Our numerical predictions for the temporal evolution of the surfactant-free crown are validated against the experimental work by Che & Matar (2017). We focus on the ‘crown-splash regime’, and we observe that the crown dynamics evolves through various stages: from the the growth of linear modes (through a RayleighPlateau instability) to the development of nonlinearities leading to primary and secondary breakup events (through droplet shedding modulated by an end-pinching mechanism). We show that the addition of surfactants does not affect the wave selection via the Rayleigh-Plateau instability. However, the presence of surfactants plays a key role in the late stages of the dynamics as soon as the ligaments are driven out from the rim. Surfactant-induced Marangoni stresses delay the end-pinching mechanisms to result in longer ligaments prior to their capillary singularity. Our results indicate that Marangoni stresses bridge the gap between adjacent protrusions promoting its collision and the merging of ligaments. Finally, we demonstrate that the addition of surfactants leads to surface rigidification and consequently to the retardation of the flow dynamics.
| Type: | Article |
|---|---|
| Title: | Impact of droplets onto surfactant-laden thin liquid films |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1017/jfm.2023.224 |
| Publisher version: | http://doi.org/10.1017/jfm.2023.224 |
| Language: | English |
| Additional information: | This work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third-party material in this article are included in the Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/ |
| 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 Mechanical Engineering |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10166124 |
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