Double Contact During Drop Impact on a Solid Under Reduced Air Pressure

Erqiang Li, Kenneth Langley, Yuan Si Tian, Peter D. Hicks, Sigurdur T Thoroddsen

Research output: Contribution to journalArticlepeer-review

41 Scopus citations

Abstract

Drops impacting on solid surfaces entrap small bubbles under their centers, owing to the lubrication pressure which builds up in the thin intervening air layer. We use ultrahigh-speed interference imaging, at 5 Mfps, to investigate how this air layer changes when the ambient air pressure is reduced below atmospheric. Both the radius and the thickness of the air disc become smaller with reduced air pressure. Furthermore, we find the radial extent of the air disc bifurcates, when the compressibility parameter exceeds similar to 25. This bifurcation is also imprinted onto some of the impacts, as a double contact. In addition to the central air disc inside the first ring contact, this is immediately followed by a second ring contact, which entraps an outer toroidal strip of air, which contracts into a ring of bubbles. We find this occurs in a regime where Navier slip, due to rarefied gas effects, enhances the rate gas can escape from the path of the droplet.
Original languageEnglish (US)
JournalPhysical Review Letters
Volume119
Issue number21
DOIs
StatePublished - Nov 20 2017

Bibliographical note

KAUST Repository Item: Exported on 2020-10-01
Acknowledged KAUST grant number(s): URF/1/2621-01-01
Acknowledgements: This study was supported by King Abdullah University of Science and Technology (KAUST) under Grant No. URF/1/2621-01-01. E. Q. L. acknowledges the Thousand Young Talents Program of China, the National Natural Science Foundation of China (Grants No. 11642019, No. 11772327, and No. 11621202) and Fundamental Research Funds for the Central Universities (Grant No. WK2090050041).

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