Bang But No Splash 252
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."
How would superfluids behave? (Score:3, Interesting)
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?
Re:We know quarks, but not this... (Score:5, Interesting)
Here's the picture (Score:5, Interesting)
http://www.hairykrishna.f2s.com/droplet.html [f2s.com]
Camera - OT (Score:2, Interesting)
I wonder how long it will take to get a digital equivalent of this camera?
Re:a very interesting question... (Score:2, Interesting)
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!
Simulations? (Score:3, Interesting)
Re:Bad link (Score:4, Interesting)
Re:We know quarks, but not this... (Score:5, Interesting)
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?
Re:We know quarks, but not this... (Score:5, Interesting)
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.
Distorted Shape (Score:4, Interesting)
WTF? This is intuitive. (Score:1, Interesting)
Slosh a large globule of water into the air and let it fall.
Watch it break apart after it reaches a certain velocity.
Wind resistance overcomes the surface tension of the water and scatters it.
I'd bet everything I owned that if you dropped the same globule of free-falling water in a vacuum it wouldn't break up like that after reaching a certain velocity.
(Though, the water would probably boil away in a vacuum or something, so substitute a different liquid for both experiments. Same effect, atomospheric resistance eventually overcoming any surface tension holding the free-falling globule together)
Applications could range from extremely fine dot-count inkjet printers to new vapor or liquid deposition manufacturing technologies. It could be a great way to make films and coatings for lots of things, including semiconductors.
Re:Isopropyl Syringe Crack Mystery... (Score:1, Interesting)
I Pushed the plunger all the way, covered the tip with my finger and pulled out the plunger to create a vacuum. When I let go of the plunger the vacuum sucked the plunger all the way back. At equilibrium there was still no perceptable air space suggesting a pretty decent vacuum for a syringe.
I gets to thinking... What if this syringe can generate a sufficient vacuum to boil water? That would be a cool demonstration.
So, not having any water within arm's reach, I grab a bottle of 70% isopropyl rubbing alcohol and suck 5 ml or so into the syringe. I push out all the air, cap the end with my finger and pull back the plunger. I see bubbles! Maybe it's boiling! But when I repeat the experiment with the syringe upside down, I don't see any bubbles, so the bubbles must have just been an air leak at that end. Oh well.
So I squirt the alcohol out of the syringe and put it on a table, and forget about it.
This morning, I notice the empty syringe on the table. I wondered if water might work better, being more viscous. Maybe some vaseline around the end could stop any leaks. But when I pick up the syringe the end of the clear plastic device that had briefly held alcohol had shattered!
First of all this hard plastic was pretty hefty - 1/8 inch thick probably. Second of all, the syringe was right where I left it, It did not get knocked down or something. Why would alcohol make it shatter?
Around the plunger, I noticed a whitish semi-translucent o-ring that had broken at one spot. Maybe it was silicone? Possibly alcohol made that gasket swell and shatter the syringe? But it was a fairly soft gasket...
Why did the syringe shatter? The world may never know....
Re:Distorted Shape (Score:4, Interesting)
NO! Large falling raindrops do not have a teardrop shape - they are flattened with the major axis roughly parallel with the ground - shaped more like a hamburger bun [orf.cx] before they break apart. Friction with the air causes the drop to distort as you indicate and high pressure is found below the drop, low above it.