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Journal of Engineering Mathematics

, Volume 111, Issue 1, pp 15–22 | Cite as

Pressure-driven plug flows between superhydrophobic surfaces of closely spaced circular bubbles

  • Ehud Yariv
  • Ory Schnitzer
Article
  • 193 Downloads

Abstract

Shear-driven flows over superhydrophobic surfaces formed of closely spaced circular bubbles are characterized by giant longitudinal slip lengths, viz., large compared with the periodicity (Schnitzer, Phys Rev Fluids 1(5):052101, 2016). This hints towards a strong superhydrophobic effect in the concomitant scenario of pressure-driven flow between two such surfaces, particularly for non-wide channels where bubble-to-bubble pitch and bubble radius are commensurate with channel width. We show here that such pressure-driven flows can be analyzed asymptotically and in closed form based on the smallness of the gaps separating the bubbles relative to the channel width (and bubble radius). We find that the flow adopts an unconventional plug profile away from the inter-bubble gaps, with the uniform velocity being asymptotically larger than the corresponding Poiseuille scale. For a given solid fraction and channel width, the net volumetric flux is maximized when the length of each semi-circular bubble-liquid interface is equal to the channel width. The plug flow identified herein cannot be obtained via a naive implementation of a Navier condition, which is indeed inapplicable for non-wide channels.

Keywords

Lubrication approximation Singular perturbations Stokes flows 

Notes

Acknowledgements

Ehud Yariv was supported by the Israel Science Foundation (Grant No. 1081/16).

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Copyright information

© Springer Science+Business Media B.V., part of Springer Nature 2018

Authors and Affiliations

  1. 1.Department of MathematicsTechnion — Israel Institute of TechnologyHaifaIsrael
  2. 2.Department of MathematicsImperial College LondonLondonUK

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