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Droplet Impacting a Cantilever: A Leaf-Raindrop System

Sean Gart1, Joseph E. Mates2, Constantine M. Megaridis2, and Sunghwan Jung1,*

  • 1Department of Engineering Science and Mechanics, Virginia Tech, Blacksburg, Virginia 24060, USA
  • 2Department of Mechanical and Industrial Engineering, University of Illinois at Chicago, Chicago, Illinois 60607, USA

  • *sunnyjsh@vt.edu
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Phys. Rev. Applied 3, 044019 – Published 30 April, 2015

DOI: https://doi.org/10.1103/PhysRevApplied.3.044019

Abstract

Previous studies show that air pollution and wind erosion, which damage a leaf’s epicuticular wax layer, can change leaf surface properties from hydrophobic to hydrophilic. However, the dynamic response of a damaged leaf to a raindrop impact has not been investigated and could clarify the direct influence of changes in wettability on early leaf abscission. In this article, we investigate how leaves with different surface properties respond to falling raindrops, viewing this as a unique system of coupled elasticity and drop dynamics. An elastic beam with tunable surface wettability properties is used as a simple leaf model. We find that wettable beams experience much higher torque and bending energy than nonwettable beams. This is because a drop sticks to a wettable beam, while a drop falls off a nonwettable beam. An analytical model using momentum balance and simple cantilever beam theory quantifies the bending energy and torque experienced by wettable and nonwettable beams. The results elucidate the potential damage caused by raindrops impacting a leaf as a function of its surface wettability and are correlated with environmental factors contributing to premature changes of leaf surface properties.

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Phys. Rev. Applied 3, 044019– Published 30 April, 2015
  • Received 17 October 2014
Article part of CHORUS

© 2015 American Physical Society

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