Stable-streamlined cavities following the impact of non-superhydrophobic spheres on water.
KAUST DepartmentHigh-Speed Fluids Imaging Laboratory
Mechanical Engineering Program
Physical Science and Engineering (PSE) Division
Permanent link to this recordhttp://hdl.handle.net/10754/656461
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AbstractThe formation of a stable-streamlined gas cavity following the impact of a heated Leidenfrost sphere on a liquid surface or a superhydrophobic sphere on water is a recently demonstrated phenomenon. A sphere encapsulated in a teardrop-shaped gas cavity was found to have near-zero hydrodynamic drag due to the self-adjusting streamlined shape and the free-slip boundary condition on the cavity interface. Here we show that such cavities can as well be formed following water impact from a sufficient height of non-superhydrophobic spheres with water contact angles between >30° and 120°. In this case the streamlined cavity is attached just above the sphere's equator, instead of entirely wrapping the sphere. Nevertheless, this sphere with attached cavity formation has near-zero drag and a predetermined free fall velocity in compliance with the Bernoulli law of potential flow. The effect of surfactant addition to the water solution is investigated. The shape and fall velocity of a sphere with streamlined cavity formation were unaffected by the addition of low surface modulus synthetic surfactants, but were destabilised when solutions containing high surface modulus surfactants, such as soaps, were used.
CitationVakarelski, I. U., Jetly, A., & Thoroddsen, S. T. (2019). Stable-streamlined cavities following the impact of non-superhydrophobic spheres on water. Soft Matter. doi:10.1039/c9sm01025d
SponsorsWe acknowledge Dr Krastanka Marinova for advice on thesurfactant solution formulation. This work was supported by King Abdullah University of Science and Technology (KAUST).
PublisherRoyal Society of Chemistry (RSC)
Except where otherwise noted, this item's license is described as Open Access Article. Published on 10 July 2019. Downloaded on 8/18/2019 11:44:43 AM. This article is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported Licence.