Not Scientific Science
Created | Updated Sep 15, 2005
Drop of Water: Reloaded
Longtime readers of Not Scientific Science may remember the article 'A Spring Called: Drop of Water', in which I explained the deformation and rebound process of a drop of water when it strikes a non-absorbent surface. 'A Spring Called: Drop of Water' was my second article for Not Scientific Science, and probably formed part of the set of articles which I most enjoyed writing. It was thus of no surprise that the minuscule article entitled 'No Slash Liquid' in the June 2005 issue of Scientific American magazine caught my eyes.
The article recounts how researchers from the University of Chicago took air in the equation to explain why splashes occurred. According to the researchers, air was an overlooked factor as far as splashes were concerned.
The researchers experimented with alcohol drops, which they released onto glass slides in a completely shut chamber with adjustable air pressure. The impacts were also filmed at a rate of 47,000 video frames per second.
The observations were impressive and completely unexpected. When at a pressure of 17% of atmospheric pressure, the drop makes absolutely no splash at all when crashing onto the glass slides. The researchers also found that lighter gases, like helium, diminished splashing and that heavier gases, krypton being one of them, enhanced it.
According to the University of Chicago team, the drop does not result in a splash on crashing because at low pressures, or with lighter gases, the compressed gas that forms between the glass surface and the drop just before the crash resists the drop's motion downwards less vigorously than it would under normal conditions (that is, atmospheric pressure and 'normal' air).
The significant resistance imposed by that compressed gas under normal conditions has the result of forcing up the drop's film edge, breaking it up to produce a nice splash. But, at reduced pressures or in heavier gases, as the compressed gas resists less vigorously, the drop's film edge is not broken and no splash occurs.
My latest ambition, I should think, is to become a splashologist — but please don't google that word just now.
This work is licenced under a Creative Commons Licence.
Other science issues (not too complicated don't you worry) can be found at:
| WORLD SCIENCE |
Not Scientific Science
Archive
