Experiments on the breakup of drop-impact crowns by Marangoni holes

Handle URI:
http://hdl.handle.net/10754/627448
Title:
Experiments on the breakup of drop-impact crowns by Marangoni holes
Authors:
Aljedaani, Abdulrahman Barakat; Wang, Chunliang; Jetly, Aditya ( 0000-0002-7835-1527 ) ; Thoroddsen, Sigurdur T. ( 0000-0001-6997-4311 )
Abstract:
We investigate experimentally the breakup of the Edgerton crown due to Marangoni instability when a highly viscous drop impacts on a thin film of lower-viscosity liquid, which also has different surface tension than the drop liquid. The presence of this low-viscosity film modifies the boundary condition, giving effective slip to the drop along the solid substrate. This allows the high-viscosity drop to form a regular bowl-shaped crown, which rises vertically away from the solid and subsequently breaks up through the formation of a multitude of Marangoni holes. Previous experiments have proposed that the breakup of the crown results from a spray of fine droplets ejected from the thin low-viscosity film on the solid, e.g. Thoroddsen et al. (J. Fluid Mech., vol. 557, 2006, pp. 63–72). These droplets can hit the inner side of the crown forming spots with lower surface tension, which drives a thinning patch leading to the hole formation. We test the validity of this assumption with close-up imaging to identify individual spray droplets, to show how they hit the crown and their lower surface tension drive the hole formation. The experiments indicate that every Marangoni-driven patch/hole is promoted by the impact of such a microdroplet. Surprisingly, in experiments with pools of higher surface tension, we also see hole formation. Here the Marangoni stress changes direction and the hole formation looks qualitatively different, with holes and ruptures forming in a repeatable fashion at the centre of each spray droplet impact. Impacts onto films of the same liquid, or onto an immiscible liquid, do not in general form holes. We furthermore characterize the effects of drop viscosity and substrate-film thickness on the overall evolution of the crown. We also measure the three characteristic velocities associated with the hole formation: i.e. the Marangoni-driven growth of the thinning patches, the rupture speed of the resulting thin films inside these patches and finally the growth rate of the fully formed holes in the crown wall.
KAUST Department:
Physical Sciences and Engineering (PSE) Division; Mechanical Engineering Program
Citation:
Aljedaani AB, Wang C, Jetly A, Thoroddsen ST (2018) Experiments on the breakup of drop-impact crowns by Marangoni holes. Journal of Fluid Mechanics 844: 162–186. Available: http://dx.doi.org/10.1017/jfm.2018.178.
Publisher:
Cambridge University Press (CUP)
Journal:
Journal of Fluid Mechanics
KAUST Grant Number:
URF/1/2621-01-01
Issue Date:
4-Apr-2018
DOI:
10.1017/jfm.2018.178
Type:
Article
ISSN:
0022-1120; 1469-7645
Sponsors:
This study was supported by King Abdullah University of Science and Technology (KAUST) under grant URF/1/2621-01-01. LW was a student intern at KAUST and performed many of the experiments.
Additional Links:
https://www.cambridge.org/core/journals/journal-of-fluid-mechanics/article/experiments-on-the-breakup-of-dropimpact-crowns-by-marangoni-holes/98F34049B4A9BA6AFBFD6603C61C685A
Appears in Collections:
Articles; Physical Sciences and Engineering (PSE) Division; Mechanical Engineering Program

Full metadata record

DC FieldValue Language
dc.contributor.authorAljedaani, Abdulrahman Barakaten
dc.contributor.authorWang, Chunliangen
dc.contributor.authorJetly, Adityaen
dc.contributor.authorThoroddsen, Sigurdur T.en
dc.date.accessioned2018-04-15T07:13:34Z-
dc.date.available2018-04-15T07:13:34Z-
dc.date.issued2018-04-04en
dc.identifier.citationAljedaani AB, Wang C, Jetly A, Thoroddsen ST (2018) Experiments on the breakup of drop-impact crowns by Marangoni holes. Journal of Fluid Mechanics 844: 162–186. Available: http://dx.doi.org/10.1017/jfm.2018.178.en
dc.identifier.issn0022-1120en
dc.identifier.issn1469-7645en
dc.identifier.doi10.1017/jfm.2018.178en
dc.identifier.urihttp://hdl.handle.net/10754/627448-
dc.description.abstractWe investigate experimentally the breakup of the Edgerton crown due to Marangoni instability when a highly viscous drop impacts on a thin film of lower-viscosity liquid, which also has different surface tension than the drop liquid. The presence of this low-viscosity film modifies the boundary condition, giving effective slip to the drop along the solid substrate. This allows the high-viscosity drop to form a regular bowl-shaped crown, which rises vertically away from the solid and subsequently breaks up through the formation of a multitude of Marangoni holes. Previous experiments have proposed that the breakup of the crown results from a spray of fine droplets ejected from the thin low-viscosity film on the solid, e.g. Thoroddsen et al. (J. Fluid Mech., vol. 557, 2006, pp. 63–72). These droplets can hit the inner side of the crown forming spots with lower surface tension, which drives a thinning patch leading to the hole formation. We test the validity of this assumption with close-up imaging to identify individual spray droplets, to show how they hit the crown and their lower surface tension drive the hole formation. The experiments indicate that every Marangoni-driven patch/hole is promoted by the impact of such a microdroplet. Surprisingly, in experiments with pools of higher surface tension, we also see hole formation. Here the Marangoni stress changes direction and the hole formation looks qualitatively different, with holes and ruptures forming in a repeatable fashion at the centre of each spray droplet impact. Impacts onto films of the same liquid, or onto an immiscible liquid, do not in general form holes. We furthermore characterize the effects of drop viscosity and substrate-film thickness on the overall evolution of the crown. We also measure the three characteristic velocities associated with the hole formation: i.e. the Marangoni-driven growth of the thinning patches, the rupture speed of the resulting thin films inside these patches and finally the growth rate of the fully formed holes in the crown wall.en
dc.description.sponsorshipThis study was supported by King Abdullah University of Science and Technology (KAUST) under grant URF/1/2621-01-01. LW was a student intern at KAUST and performed many of the experiments.en
dc.publisherCambridge University Press (CUP)en
dc.relation.urlhttps://www.cambridge.org/core/journals/journal-of-fluid-mechanics/article/experiments-on-the-breakup-of-dropimpact-crowns-by-marangoni-holes/98F34049B4A9BA6AFBFD6603C61C685Aen
dc.subjectCapillary flowsen
dc.subjectdropsen
dc.subjectinterfacial flows (free surface)en
dc.titleExperiments on the breakup of drop-impact crowns by Marangoni holesen
dc.typeArticleen
dc.contributor.departmentPhysical Sciences and Engineering (PSE) Divisionen
dc.contributor.departmentMechanical Engineering Programen
dc.identifier.journalJournal of Fluid Mechanicsen
kaust.authorAljedaani, Abdulrahman Barakaten
kaust.authorWang, Chunliangen
kaust.authorJetly, Adityaen
kaust.authorThoroddsen, Sigurdur T.en
kaust.grant.numberURF/1/2621-01-01en
All Items in KAUST are protected by copyright, with all rights reserved, unless otherwise indicated.