Impact of ultra-viscous drops: air-film gliding and extreme wetting

Handle URI:
http://hdl.handle.net/10754/622896
Title:
Impact of ultra-viscous drops: air-film gliding and extreme wetting
Authors:
Langley, Kenneth ( 0000-0001-6999-8727 ) ; Li, Erqiang ( 0000-0002-5003-0756 ) ; Thoroddsen, Sigurdur T. ( 0000-0001-6997-4311 )
Abstract:
A drop impacting on a solid surface must push away the intervening gas layer before making contact. This entails a large lubricating air pressure which can deform the bottom of the drop, thus entrapping a bubble under its centre. For a millimetric water drop, the viscous-dominated flow in the thin air layer counteracts the inertia of the drop liquid. For highly viscous drops the viscous stresses within the liquid also affect the interplay between the drop and the gas. Here the drop also forms a central dimple, but its outer edge is surrounded by an extended thin air film, without contacting the solid. This is in sharp contrast with impacts of lower-viscosity drops where a kink in the drop surface forms at the edge of the central disc and makes a circular contact with the solid. Larger drop viscosities make the central air dimple thinner. The thin outer air film subsequently ruptures at numerous random locations around the periphery, when it reaches below 150 nm thickness. This thickness we measure using high-speed two-colour interferometry. The wetted circular contacts expand rapidly, at orders of magnitude larger velocities than would be predicted by a capillary-viscous balance. The spreading velocity of the wetting spots is independent of the liquid viscosity. This may suggest enhanced slip of the contact line, assisted by rarefied-gas effects, or van der Waals forces in what we call extreme wetting. Myriads of micro-bubbles are captured between the local wetting spots.
KAUST Department:
Clean Combustion Research Center; Physical Sciences and Engineering (PSE) Division
Citation:
Langley K, Li EQ, Thoroddsen ST (2017) Impact of ultra-viscous drops: air-film gliding and extreme wetting. Journal of Fluid Mechanics 813: 647–666. Available: http://dx.doi.org/10.1017/jfm.2016.840.
Publisher:
Cambridge University Press (CUP)
Journal:
Journal of Fluid Mechanics
Issue Date:
23-Jan-2017
DOI:
10.1017/jfm.2016.840
Type:
Article
ISSN:
0022-1120; 1469-7645
Sponsors:
The work reported herein was funded by King Abdullah University of Science and Technology (KAUST).
Additional Links:
https://www.cambridge.org/core/journals/journal-of-fluid-mechanics/article/div-classtitleimpact-of-ultra-viscous-drops-air-film-gliding-and-extreme-wettingdiv/798BDD556D6008324CB300EC56F80F16
Appears in Collections:
Articles; Physical Sciences and Engineering (PSE) Division; Clean Combustion Research Center

Full metadata record

DC FieldValue Language
dc.contributor.authorLangley, Kennethen
dc.contributor.authorLi, Erqiangen
dc.contributor.authorThoroddsen, Sigurdur T.en
dc.date.accessioned2017-02-15T08:32:15Z-
dc.date.available2017-02-15T08:32:15Z-
dc.date.issued2017-01-23en
dc.identifier.citationLangley K, Li EQ, Thoroddsen ST (2017) Impact of ultra-viscous drops: air-film gliding and extreme wetting. Journal of Fluid Mechanics 813: 647–666. Available: http://dx.doi.org/10.1017/jfm.2016.840.en
dc.identifier.issn0022-1120en
dc.identifier.issn1469-7645en
dc.identifier.doi10.1017/jfm.2016.840en
dc.identifier.urihttp://hdl.handle.net/10754/622896-
dc.description.abstractA drop impacting on a solid surface must push away the intervening gas layer before making contact. This entails a large lubricating air pressure which can deform the bottom of the drop, thus entrapping a bubble under its centre. For a millimetric water drop, the viscous-dominated flow in the thin air layer counteracts the inertia of the drop liquid. For highly viscous drops the viscous stresses within the liquid also affect the interplay between the drop and the gas. Here the drop also forms a central dimple, but its outer edge is surrounded by an extended thin air film, without contacting the solid. This is in sharp contrast with impacts of lower-viscosity drops where a kink in the drop surface forms at the edge of the central disc and makes a circular contact with the solid. Larger drop viscosities make the central air dimple thinner. The thin outer air film subsequently ruptures at numerous random locations around the periphery, when it reaches below 150 nm thickness. This thickness we measure using high-speed two-colour interferometry. The wetted circular contacts expand rapidly, at orders of magnitude larger velocities than would be predicted by a capillary-viscous balance. The spreading velocity of the wetting spots is independent of the liquid viscosity. This may suggest enhanced slip of the contact line, assisted by rarefied-gas effects, or van der Waals forces in what we call extreme wetting. Myriads of micro-bubbles are captured between the local wetting spots.en
dc.description.sponsorshipThe work reported herein was funded by King Abdullah University of Science and Technology (KAUST).en
dc.publisherCambridge University Press (CUP)en
dc.relation.urlhttps://www.cambridge.org/core/journals/journal-of-fluid-mechanics/article/div-classtitleimpact-of-ultra-viscous-drops-air-film-gliding-and-extreme-wettingdiv/798BDD556D6008324CB300EC56F80F16en
dc.subjectContact linesen
dc.subjectdrops and bubblesen
dc.subjectthin filmsen
dc.titleImpact of ultra-viscous drops: air-film gliding and extreme wettingen
dc.typeArticleen
dc.contributor.departmentClean Combustion Research Centeren
dc.contributor.departmentPhysical Sciences and Engineering (PSE) Divisionen
dc.identifier.journalJournal of Fluid Mechanicsen
kaust.authorLangley, Kennethen
kaust.authorLi, Erqiangen
kaust.authorThoroddsen, Sigurdur T.en
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