Propagation of capillary waves and ejection of small droplets in rapid droplet spreading

Handle URI:
http://hdl.handle.net/10754/562126
Title:
Propagation of capillary waves and ejection of small droplets in rapid droplet spreading
Authors:
Ding, Hang; Li, Erqiang ( 0000-0002-5003-0756 ) ; Zhang, F. H.; Sui, Yi; Spelt, Peter D M; Thoroddsen, Sigurdur T. ( 0000-0001-6997-4311 )
Abstract:
A new regime of droplet ejection following the slow deposition of drops onto a near-complete wetting solid substrate is identified in experiments and direct numerical simulations; a coalescence cascade subsequent to pinch-off is also observed for the first time. Results of numerical simulations indicate that the propagation of capillary waves that lead to pinch-off is closely related to the self-similar behaviour observed in the inviscid recoil of droplets, and that motions of the crests and troughs of capillary waves along the interface do not depend on the wettability and surface tension (or Ohnesorge number). The simulations also show that a self-similar theory for universal pinch-off can be used for the time evolution of the pinching neck. However, although good agreement is also found with the double-cone shape of the pinching neck for droplet ejection in drop deposition on a pool of the same liquid, substantial deviations are observed in such a comparison for droplet ejection in rapid drop spreading (including the newly identified regime). This deviation is shown to result from interference by the solid substrate, a rapid downwards acceleration of the top of the drop surface and the rapid spreading process. The experiments also confirm non-monotonic spreading behaviour observed previously only in numerical simulations, and suggest substantial inertial effects on the relation between an apparent contact angle and the dimensionless contact-line speed. © 2012 Cambridge University Press.
KAUST Department:
Physical Sciences and Engineering (PSE) Division; Clean Combustion Research Center; Mechanical Engineering Program; High-Speed Fluids Imaging Laboratory
Publisher:
Cambridge University Press (CUP)
Journal:
Journal of Fluid Mechanics
Issue Date:
12-Mar-2012
DOI:
10.1017/jfm.2012.49
Type:
Article
ISSN:
00221120
Sponsors:
H.D. was supported by 100 Talents Program of The Chinese Academy of Sciences and the National Natural Science Foundation of China (Grant No. 11172294). E.Q.L. and S.T.T. were partly supported by KAUST-BERKELEY AEA grant 7000000024. Y.S. and P.D.M.S. were supported from EPSRC under grant numbers EP/E046029/1.
Appears in Collections:
Articles; Physical Sciences and Engineering (PSE) Division; Mechanical Engineering Program; Clean Combustion Research Center

Full metadata record

DC FieldValue Language
dc.contributor.authorDing, Hangen
dc.contributor.authorLi, Erqiangen
dc.contributor.authorZhang, F. H.en
dc.contributor.authorSui, Yien
dc.contributor.authorSpelt, Peter D Men
dc.contributor.authorThoroddsen, Sigurdur T.en
dc.date.accessioned2015-08-03T09:45:25Zen
dc.date.available2015-08-03T09:45:25Zen
dc.date.issued2012-03-12en
dc.identifier.issn00221120en
dc.identifier.doi10.1017/jfm.2012.49en
dc.identifier.urihttp://hdl.handle.net/10754/562126en
dc.description.abstractA new regime of droplet ejection following the slow deposition of drops onto a near-complete wetting solid substrate is identified in experiments and direct numerical simulations; a coalescence cascade subsequent to pinch-off is also observed for the first time. Results of numerical simulations indicate that the propagation of capillary waves that lead to pinch-off is closely related to the self-similar behaviour observed in the inviscid recoil of droplets, and that motions of the crests and troughs of capillary waves along the interface do not depend on the wettability and surface tension (or Ohnesorge number). The simulations also show that a self-similar theory for universal pinch-off can be used for the time evolution of the pinching neck. However, although good agreement is also found with the double-cone shape of the pinching neck for droplet ejection in drop deposition on a pool of the same liquid, substantial deviations are observed in such a comparison for droplet ejection in rapid drop spreading (including the newly identified regime). This deviation is shown to result from interference by the solid substrate, a rapid downwards acceleration of the top of the drop surface and the rapid spreading process. The experiments also confirm non-monotonic spreading behaviour observed previously only in numerical simulations, and suggest substantial inertial effects on the relation between an apparent contact angle and the dimensionless contact-line speed. © 2012 Cambridge University Press.en
dc.description.sponsorshipH.D. was supported by 100 Talents Program of The Chinese Academy of Sciences and the National Natural Science Foundation of China (Grant No. 11172294). E.Q.L. and S.T.T. were partly supported by KAUST-BERKELEY AEA grant 7000000024. Y.S. and P.D.M.S. were supported from EPSRC under grant numbers EP/E046029/1.en
dc.publisherCambridge University Press (CUP)en
dc.subjectcapillary wavesen
dc.subjectcontact linesen
dc.subjectdropsen
dc.titlePropagation of capillary waves and ejection of small droplets in rapid droplet spreadingen
dc.typeArticleen
dc.contributor.departmentPhysical Sciences and Engineering (PSE) Divisionen
dc.contributor.departmentClean Combustion Research Centeren
dc.contributor.departmentMechanical Engineering Programen
dc.contributor.departmentHigh-Speed Fluids Imaging Laboratoryen
dc.identifier.journalJournal of Fluid Mechanicsen
dc.contributor.institutionUniv London Imperial Coll Sci Technol & Med, Dept Chem Engn, London SW7 2AZ, Englanden
dc.contributor.institutionUniv Lyon 1, Dept Mecan, F-69134 Ecully, Franceen
dc.contributor.institutionCNRS, Lab Mecan Fluides & Acoust, F-69134 Ecully, Franceen
dc.contributor.institutionUniv Sci & Technol China, Dept Modern Mech, Hefei 230027, Peoples R Chinaen
dc.contributor.institutionUniv Calif Santa Barbara, Dept Chem Engn, Santa Barbara, CA 93106 USAen
dc.contributor.institutionNatl Univ Singapore, Dept Mech Engn, Singapore 119260, Singaporeen
dc.contributor.institutionNatl Univ Singapore, Singapore MIT Alliance, Singapore 117576, Singaporeen
kaust.authorLi, Erqiangen
kaust.authorThoroddsen, Sigurdur T.en
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