leidenfrost drop, sideview
looking underneath the drop with interference imaging
When a drop of liquid is placed on a very hot surface, an amazing phenomenon occurs. Above a certain temperature, instead of boiling rapidly, the drop will levitate on a thin cushion of vapor. This effect is known as the Leidenfrost effect, and can be easily visualized when small water drops float across a hot frying pan. Underneath the drop, there is a small vapor pocket created by the evaporation of the liquid. We are currently studying this thin vapor layer using laser light interference coupled with high-speed video. Using this technique, we can clearly see the neck where the drop is closest to the interface, as well as many fluctuations and structure that is not visible in the images from the side or in the simple model of the vapor cushion.
“Dynamics of Vapor Layer Under a Leidenfrost Drop”, T. Caswell, Phys. Rev. E, 90, 013014 (2014)
“Geometry of the vapor layer under a leidenfrost drop.”, J. C. Burton, A. L. Sharpe, R. C. A. van der Veen, A. Franco, S. R. Nagel, Phys. Rev. Lett., 109, 074301 (2012).