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Effects of Super-Hydrophobic Coatings on Free Falling Spheres


The present work deals with a joint experimental investigationof free falling super-hydrophobic spheres in pure water at rest.The results derive from a collaboration between the Universityof Orl ́eans (France) and the Monash University (Australia). Thesuper-hydrophobic coatings have the ability, once immersedinto water, to reduce the contact area between the liquid andthe solid surface by entrapping an air layer in the surface rough-ness. We thus investigate a possible effect of this feature onthe hydrodynamic drag of spheres, focusing on the terminal ve-locity region. Surprisingly, the hydrodynamic performance ofsuper-hydrophobic coatings depends on the analysed Reynoldsnumber regime. The drag increase evidenced for the small di-ameter spheres tends progressively to turn into a drag attenu-ation for the largest diameters spheres. A possible connectionbetween the hydrodynamic performance and the deformation ofthe air layer encapsulating the coated spheres is proposed.
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hal-02082573 , version 1 (28-03-2019)


  • HAL Id : hal-02082573 , version 1


Marco Castagna, M. P. Eisfelder, H. Taylor, Nicolas Mazellier, Azeddine Kourta, et al.. Effects of Super-Hydrophobic Coatings on Free Falling Spheres. 21st Australasian Fluid Mechanics Conference, Dec 2018, Adelaide, Australia. ⟨hal-02082573⟩
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