Drag crisis moderation by thin air layers sustained on superhydrophobic spheres falling in water

Handle URI:
http://hdl.handle.net/10754/627008
Title:
Drag crisis moderation by thin air layers sustained on superhydrophobic spheres falling in water
Authors:
Jetly, Aditya ( 0000-0002-7835-1527 ) ; Vakarelski, Ivan Uriev ( 0000-0001-9244-9160 ) ; Thoroddsen, Sigurdur T. ( 0000-0001-6997-4311 )
Abstract:
We investigate the effect of thin air layers naturally sustained on superhydrophobic surfaces on the terminal velocity and drag force of metallic spheres free falling in water. The surface of 20 mm to 60 mm steel or tungsten-carbide spheres is rendered superhydrophobic by a simple coating process that uses commercially available hydrophobic agent. By comparing the free fall of unmodified spheres and superhydrophobic spheres in a 2.5 meters tall water tank, It is demonstrated that even a very thin air layer (~ 1 – 2 μm) that covers the freshly dipped superhydrophobic sphere, can reduce the drag force on the spheres by up to 80 %, at Reynolds numbers 105 - 3×105 , owing to an early drag crisis transition. This study complements prior investigations on the drag reduction efficiency of model gas layers sustained on heated metal spheres falling in liquid by the Leidenfrost effect. The drag reduction effects are expected to have significant implication for the development of sustainable air-layer-based energy saving technologies.
KAUST Department:
Physical Sciences and Engineering (PSE) Division; Mechanical Engineering Program
Citation:
Jetly A, Vakarelski IU, Thoroddsen ST (2018) Drag crisis moderation by thin air layers sustained on superhydrophobic spheres falling in water. Soft Matter. Available: http://dx.doi.org/10.1039/c7sm01904a.
Publisher:
Royal Society of Chemistry (RSC)
Journal:
Soft Matter
Issue Date:
22-Jan-2018
DOI:
10.1039/c7sm01904a
Type:
Article
ISSN:
1744-683X; 1744-6848
Sponsors:
This work was supported by the King Abdullah University of Science and Technology (KAUST). We acknowledge Mr. Ziqiang Yang for the assistance in the some of the experiments. The AFM imaging was performed in the KAUST Microfluidics Thrust Area Labs.
Additional Links:
http://pubs.rsc.org/en/Content/ArticleLanding/2018/SM/C7SM01904A#!divAbstract
Appears in Collections:
Articles; Physical Sciences and Engineering (PSE) Division; Mechanical Engineering Program

Full metadata record

DC FieldValue Language
dc.contributor.authorJetly, Adityaen
dc.contributor.authorVakarelski, Ivan Urieven
dc.contributor.authorThoroddsen, Sigurdur T.en
dc.date.accessioned2018-02-01T11:45:54Z-
dc.date.available2018-02-01T11:45:54Z-
dc.date.issued2018-01-22en
dc.identifier.citationJetly A, Vakarelski IU, Thoroddsen ST (2018) Drag crisis moderation by thin air layers sustained on superhydrophobic spheres falling in water. Soft Matter. Available: http://dx.doi.org/10.1039/c7sm01904a.en
dc.identifier.issn1744-683Xen
dc.identifier.issn1744-6848en
dc.identifier.doi10.1039/c7sm01904aen
dc.identifier.urihttp://hdl.handle.net/10754/627008-
dc.description.abstractWe investigate the effect of thin air layers naturally sustained on superhydrophobic surfaces on the terminal velocity and drag force of metallic spheres free falling in water. The surface of 20 mm to 60 mm steel or tungsten-carbide spheres is rendered superhydrophobic by a simple coating process that uses commercially available hydrophobic agent. By comparing the free fall of unmodified spheres and superhydrophobic spheres in a 2.5 meters tall water tank, It is demonstrated that even a very thin air layer (~ 1 – 2 μm) that covers the freshly dipped superhydrophobic sphere, can reduce the drag force on the spheres by up to 80 %, at Reynolds numbers 105 - 3×105 , owing to an early drag crisis transition. This study complements prior investigations on the drag reduction efficiency of model gas layers sustained on heated metal spheres falling in liquid by the Leidenfrost effect. The drag reduction effects are expected to have significant implication for the development of sustainable air-layer-based energy saving technologies.en
dc.description.sponsorshipThis work was supported by the King Abdullah University of Science and Technology (KAUST). We acknowledge Mr. Ziqiang Yang for the assistance in the some of the experiments. The AFM imaging was performed in the KAUST Microfluidics Thrust Area Labs.en
dc.publisherRoyal Society of Chemistry (RSC)en
dc.relation.urlhttp://pubs.rsc.org/en/Content/ArticleLanding/2018/SM/C7SM01904A#!divAbstracten
dc.rightsArchived with thanks to Soft Matteren
dc.titleDrag crisis moderation by thin air layers sustained on superhydrophobic spheres falling in wateren
dc.typeArticleen
dc.contributor.departmentPhysical Sciences and Engineering (PSE) Divisionen
dc.contributor.departmentMechanical Engineering Programen
dc.identifier.journalSoft Matteren
dc.eprint.versionPost-printen
kaust.authorJetly, Adityaen
kaust.authorVakarelski, Ivan Urieven
kaust.authorThoroddsen, Sigurdur T.en
All Items in KAUST are protected by copyright, with all rights reserved, unless otherwise indicated.