Probing the nanoscale: the first contact of an impacting drop

dc.contributor.affiliationKing Abdullah University of Science and Technology (KAUST)
dc.contributor.authorLi, Erqiang
dc.contributor.authorVakarelski, Ivan Uriev
dc.contributor.authorThoroddsen, Sigurdur T
dc.contributor.departmentClean Combustion Research Center
dc.contributor.departmentHigh-Speed Fluids Imaging Laboratory
dc.contributor.departmentMechanical Engineering Program
dc.contributor.departmentPhysical Science and Engineering (PSE) Division
dc.date.accessioned2015-12-14T08:09:30Z
dc.date.available2015-12-14T08:09:30Z
dc.date.issued2015-11-16
dc.date.published-online2015-11-16
dc.date.published-print2015-12
dc.description.abstractWhen a drop impacts onto a solid surface, the lubrication pressure in the air deforms its bottom into a dimple. This makes the initial contact with the substrate occur not at a point but along a ring, thereby entrapping a central disc of air. We use ultra-high-speed imaging, with 200 ns time resolution, to observe the structure of this first contact between the liquid and a smooth solid surface. For a water drop impacting onto regular glass we observe a ring of microbubbles, due to multiple initial contacts just before the formation of the fully wetted outer section. These contacts are spaced by a few microns and quickly grow in size until they meet, thereby leaving behind a ring of microbubbles marking the original air-disc diameter. On the other hand, no microbubbles are left behind when the drop impacts onto molecularly smooth mica sheets. We thereby conclude that the localized contacts are due to nanometric roughness of the glass surface, and the presence of the microbubbles can therefore distinguish between glass with 10 nm roughness and perfectly smooth glass. We contrast this entrapment topology with the initial contact of a drop impacting onto a film of extremely viscous immiscible liquid, where the initial contact appears to be continuous along the ring. Here, an azimuthal instability occurs during the rapid contraction at the triple line, also leaving behind microbubbles. For low impact velocities the nature of the initial contact changes to one initiated by ruptures of a thin lubricating air film.
dc.eprint.versionPost-print
dc.identifier.citationProbing the nanoscale: the first contact of an impacting drop 2015, 785 Journal of Fluid Mechanics
dc.identifier.doi10.1017/jfm.2015.643
dc.identifier.issn0022-1120
dc.identifier.issn1469-7645
dc.identifier.journalJournal of Fluid Mechanics
dc.identifier.urihttp://hdl.handle.net/10754/583813
dc.language.isoen
dc.publisherCambridge University Press (CUP)
dc.relation.urlhttp://www.journals.cambridge.org/abstract_S0022112015006436
dc.rightsArchived with thanks to Journal of Fluid Mechanics
dc.subjectcontact lines
dc.subjectdrops and bubbles
dc.subjectfingering instability
dc.titleProbing the nanoscale: the first contact of an impacting drop
dc.typeArticle
display.details.left<span><h5>Type</h5>Article<br><br><h5>Authors</h5><a href="https://repository.kaust.edu.sa/search?query=orcid.id:0000-0002-5003-0756&spc.sf=dc.date.issued&spc.sd=DESC">Li, Erqiang</a> <a href="https://orcid.org/0000-0002-5003-0756" target="_blank"><img src="https://repository.kaust.edu.sa/server/api/core/bitstreams/82a625b4-ed4b-40c8-865a-d6a5225a26a4/content" width="16" height="16"/></a><br><a href="https://repository.kaust.edu.sa/search?query=orcid.id:0000-0001-9244-9160&spc.sf=dc.date.issued&spc.sd=DESC">Vakarelski, Ivan Uriev</a> <a href="https://orcid.org/0000-0001-9244-9160" target="_blank"><img src="https://repository.kaust.edu.sa/server/api/core/bitstreams/82a625b4-ed4b-40c8-865a-d6a5225a26a4/content" width="16" height="16"/></a><br><a href="https://repository.kaust.edu.sa/search?query=orcid.id:0000-0001-6997-4311&spc.sf=dc.date.issued&spc.sd=DESC">Thoroddsen, Sigurdur T</a> <a href="https://orcid.org/0000-0001-6997-4311" target="_blank"><img src="https://repository.kaust.edu.sa/server/api/core/bitstreams/82a625b4-ed4b-40c8-865a-d6a5225a26a4/content" width="16" height="16"/></a><br><br><h5>KAUST Department</h5><a href="https://repository.kaust.edu.sa/search?spc.sf=dc.date.issued&spc.sd=DESC&f.department=Clean Combustion Research Center,equals">Clean Combustion Research Center</a><br><a href="https://repository.kaust.edu.sa/search?spc.sf=dc.date.issued&spc.sd=DESC&f.department=High-Speed Fluids Imaging Laboratory,equals">High-Speed Fluids Imaging Laboratory</a><br><a href="https://repository.kaust.edu.sa/search?spc.sf=dc.date.issued&spc.sd=DESC&f.department=Mechanical Engineering Program,equals">Mechanical Engineering Program</a><br><a href="https://repository.kaust.edu.sa/search?spc.sf=dc.date.issued&spc.sd=DESC&f.department=Physical Science and Engineering (PSE) Division,equals">Physical Science and Engineering (PSE) Division</a><br><br><h5>Online Publication Date</h5>2015-11-16<br><br><h5>Print Publication Date</h5>2015-12<br><br><h5>Date</h5>2015-11-16</span>
display.details.right<span><h5>Abstract</h5>When a drop impacts onto a solid surface, the lubrication pressure in the air deforms its bottom into a dimple. This makes the initial contact with the substrate occur not at a point but along a ring, thereby entrapping a central disc of air. We use ultra-high-speed imaging, with 200 ns time resolution, to observe the structure of this first contact between the liquid and a smooth solid surface. For a water drop impacting onto regular glass we observe a ring of microbubbles, due to multiple initial contacts just before the formation of the fully wetted outer section. These contacts are spaced by a few microns and quickly grow in size until they meet, thereby leaving behind a ring of microbubbles marking the original air-disc diameter. On the other hand, no microbubbles are left behind when the drop impacts onto molecularly smooth mica sheets. We thereby conclude that the localized contacts are due to nanometric roughness of the glass surface, and the presence of the microbubbles can therefore distinguish between glass with 10 nm roughness and perfectly smooth glass. We contrast this entrapment topology with the initial contact of a drop impacting onto a film of extremely viscous immiscible liquid, where the initial contact appears to be continuous along the ring. Here, an azimuthal instability occurs during the rapid contraction at the triple line, also leaving behind microbubbles. For low impact velocities the nature of the initial contact changes to one initiated by ruptures of a thin lubricating air film.<br><br><h5>Citation</h5>Probing the nanoscale: the first contact of an impacting drop 2015, 785 Journal of Fluid Mechanics<br><br><h5>Publisher</h5><a href="https://repository.kaust.edu.sa/search?spc.sf=dc.date.issued&spc.sd=DESC&f.publisher=Cambridge University Press (CUP),equals">Cambridge University Press (CUP)</a><br><br><h5>Journal</h5><a href="https://repository.kaust.edu.sa/search?spc.sf=dc.date.issued&spc.sd=DESC&f.journal=Journal of Fluid Mechanics,equals">Journal of Fluid Mechanics</a><br><br><h5>DOI</h5><a href="https://doi.org/10.1017/jfm.2015.643">10.1017/jfm.2015.643</a><br><br><h5>Additional Links</h5>http://www.journals.cambridge.org/abstract_S0022112015006436</span>
kaust.personLi, Erqiang
kaust.personVakarelski, Ivan Uriev
kaust.personThoroddsen, Sigurdur T.
orcid.authorLi, Erqiang::0000-0002-5003-0756
orcid.authorVakarelski, Ivan Uriev::0000-0001-9244-9160
orcid.authorThoroddsen, Sigurdur T::0000-0001-6997-4311
orcid.id0000-0001-6997-4311
orcid.id0000-0001-9244-9160
orcid.id0000-0002-5003-0756
refterms.dateFOA2016-05-16T00:00:00Z
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