Leidenfrost vapour layer moderation of the drag crisis and trajectories of superhydrophobic and hydrophilic spheres falling in water
KAUST DepartmentClean Combustion Research Center
High-Speed Fluids Imaging Laboratory
Mechanical Engineering Program
Physical Science and Engineering (PSE) Division
Permanent link to this recordhttp://hdl.handle.net/10754/563225
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AbstractWe investigate the dynamic effects of a Leidenfrost vapour layer sustained on the surface of heated steel spheres during free fall in water. We find that a stable vapour layer sustained on the textured superhydrophobic surface of spheres falling through 95 °C water can reduce the hydrodynamic drag by up to 75% and stabilize the sphere trajectory for the Reynolds number between 104 and 106, spanning the drag crisis in the absence of the vapour layer. For hydrophilic spheres under the same conditions, the transition to drag reduction and trajectory stability occurs abruptly at a temperature different from the static Leidenfrost point. The observed drag reduction effects are attributed to the disruption of the viscous boundary layer by the vapour layer whose thickness depends on the water temperature. Both the drag reduction and the trajectory stabilization effects are expected to have significant implications for development of sustainable vapour layer based technologies. © the Partner Organisations 2014.
CitationVakarelski, I. U., Chan, D. Y. C., & Thoroddsen, S. T. (2014). Leidenfrost vapour layer moderation of the drag crisis and trajectories of superhydrophobic and hydrophilic spheres falling in water. Soft Matter, 10(31), 5662–5668. doi:10.1039/c4sm00368c
SponsorsWe acknowledge G. D. Li from the KAUST Solar and Photovoltaics Research Center for assisting in the water tank and heater device design, and the KAUST Machine Workshop for the support in setting the experiments. This work is support in part by an Australian Research Council Discovery Project Grant to DYCC.
PublisherRoyal Society of Chemistry (RSC)
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