Leidenfrost effect drops found to be self-propelled

phys.org | 9/12/2018 | Staff
ajoy26 (Posted by) Level 3
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A team of researchers at Physique et Mécanique des Milieux Hétérogènes in France has found that Leidenfrost effect drops move around on a hot pan because they are self-propelled. In their paper published in the journal Nature Physics, the group describes their study of the drops and what they found.

When drops of water land on a hot surface they begin moving around in the pan like a hockey puck on ice. Prior research has shown the slipperiness of the drops is due to a thin layer of steam that is created between the drop and the pan—causing the drop to be levitated. As to why the drop moves without prompting, prior researchers have suggested it is due to slight bits of air movement or gravity acting on them. In this new effort, the researchers have found that there is another force involved.

Drops - Apparent - Cause - Researchers - Experiment

To find out why the drops move without apparent cause, the researchers set up an experiment that involved placing a pan on a hot plate surrounded by high-speed cameras which were attached to motion-tracking software. To find out what goes on inside of the droplets, the group injected tiny glass spheres into a small sample of water which was used for generating droplets.

In examining the results on their computer screen, the researchers found that larger drops behaved as expected—the glass spheres flowed in a smooth manner and the drops on the hot plate hardly moved. But as the drops on the pan grew smaller due to evaporation, they flattened out...
(Excerpt) Read more at: phys.org
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