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Bang But No Splash
BishopBerkeley writes "When a drop of ethanol is dropped on a surface at low pressures (1/5 atmosphere or less), it makes no splash. Science offers a brief synopsis and fascinating pictures of the phenomenon. The results seem to confirm the (perhaps counterintuitive) prediction that more viscous liquids are more likely to splash, not less likely . Links to the researchers' home page at U of Chicago (as of now, the site is timing out) and pdf version of the article on arxiv can be found on the Science page also."
It would be interesting to investigate how superfluids behave.
Since the article hints that the more viscosity, the lower the pressure must be to avoid splashing of the droplet, would superfluids (which have no viscosity at all) behave as expected even under the atmospheric pressure, or even a higher pressure?
Offhand, why are they using ethanol and not water for their study though?
Well, to be fair to the upper crust Elizabethan gentleman scientists of yore, photography wouldn't be invented for another two hundred years, and high speed emulsions for some decades after that. Now those 20th century scientists -- thats a different kettle of fish.
Post may contain irony: discontinue use if experiencing mood swings, nausea or elevated blood pressure.
http://www.hairykrishna.f2s.com/droplet.html
"Physics is to math as sex is to masturbation." -R. Feynman
Off the top of my head... as the liquid is moving horizontally along the surface, it encounters air molecules, which causes the leading edge of the surface to pile up. As it piles up, it acquires the vertical component. Less air pressure -> less air molecules encountered -> less piling up -> less vertical component -> less splashing.
Friction with the surface will slow down the liquid at the surface, but without the air resistance liquid not in contact with the surface just flows over the slower liquid at the surface and so doesn't pile up.
Of course, IANAP, so this worth exactly what you paid for it. If, on the other hand, I happen to be right -- remember, you heard it here first!
What would be great is to check this phenomenon out with computer simulation. It might be tough to set up though, since you'd have to deal with a compressible gas phase and incompressible fluid phase, and keep track of the fluid surface to account for surface tension. I'm sure it could be done though. Axisymmetric simulation would probably be fine to start off.
The world is everything that is the case
The OP is probably at an institution where they have a site subscription to Science (most American universities worth their salt do, for example), so when they go to the link they get the article right away. If Hemos is somewhere that has a site subscription to Science, he'd get the same thing, and it would be a relatively subtle thing to figure out whether nonsubscribers can read the article or not.
A small balloon is inflated in atmospheric pressure until it pops. The resulting fragments are a few large pieces of latex.
A simmilar balloon is inflated by tying it off, placing it in a bell jar, and evacuating the jar. When the balloon pops, the result is a shredded mess of many small pieces of latex.
The guy at the museum who showed this demonstration couldn't explain to me why it did this. He just kept saying, "It pops everywhere at once". Okay, but why?
"Uh... yeah, Brain, but where are we going to find rubber pants our size?" --Pinky
Given no a priori knowledge of this experiment, I could come up with convincing thought experiments and analogies to explain either possible outcome (low viscosity or high viscosity being less likely to splash).
For example, what happens when a ball of soft putty drops on a surface? It definitely doesn't produce an apparent splash. The "intuitive" interpretation might be, then, that high viscosity liquids are less able to splash, based on our experience with a large, viscous semisolid.
~Idarubicin
I noticed that the drop that made the biggest splash was already distorted before impact. The drop that didn't make a splash was a perfect sphere up until the moment of impact.