# Help on Leidenfrost effect

1. Mar 31, 2004

### Tamerlane

First of all, let me say that i'm a french [in the way that i speak french] student and most probably my sentences will not be as accurate as they should, excuse me in advance.

To make a long story short, the Leidenfrost effect makes a water drop to stop "boiling" at temperatures higher than 240 Celsius. The principle is as follows: the suddent heating of the water (when it falls on the surface) immediately creates a vapor layer between the liquified water and the surface.

Note: we have roughly measured the actual temperature of the water at around 80 celsius.

The same effect happens with a particular plastic surface that as been "polished" (or scratched) with an extremely thin sandpaper OR a surface covered with teflon => there is small "bubbles" of air that gets trapped between the real surface and the water.

Anyway, what interests me and my group is that when you heat the water ; our optimal temperature (for the oscillating mode we concentrated on) is about 410 celsius, at that point and from a very particular volume of water [the drop constantly evaporate], it starts oscillating at a frequency of about 10Hz and increasing. At that point, the drop has a rounded triangular shape, but it's so fast, you see 6 and arguably 8 tip to the "star" it forms.

Now, i'd like to know if anybody has ever heard of or work on such thing, we'd especially like to know what exactly happens, what makes the water turn on itself or oscillate [we're not even sure about the movement of the molecules within the drop]. If there is any formula that exists to describe such phenomenon or anything else.

Also, we are being told it has something to do with surface tension, anyone can help?

Thank you

Note to anyone who might wonder: i've put this message on 2 boards