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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."
Fascinating. ----- Ut Tensio, Sic Vis
Ut Tensio, Sic Vis
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Full Text : Cho,Sucking Away the Splatter, ScienceNOW 2005: 4
Uh oh. Someone left some ethanol next to bored scientists again.
People like my friends know the right thing to do, but it appears that this knowledge is not common enough.
The creatures outside looked from Alt-Right to Antifa; but already it was impossible to say which was which.
" Your Subscription does not grant access to this item: Full Text : Cho,Sucking Away the Splatter, ScienceNOW 2005: 4"
Sounds like a whole different kind of webpage..
You cant fight in here, its a war room!
When a few drops of ethyl alcohol are dropped into a low-tolerance system, you get bangs, splashes, crashes, all kinds of stuff.
More study is clearly needed.
Click here to see.
Meh.
Isn't it amazing that we're investigating quarks but haven't yet fully understood the properties of athmosphere and vacuum? We could have found those phenomena 400 years ago, but no...
Makes one wonder what else the laws of physics are hiding from us yet... and whether we have really tried to analyse physics systematically enough.
(1 seems to be subscription only, other is alredy /.?)
Lets continue doing those experiments with alcohol ourself. In a plane. Mixed with lots of water (beer) , mixed with less water (jenever). Ans splashing.
Anything more useful to report about alcohol abuse?
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?
Sucking Away the Splatter
LOS ANGELES--Nature may abhor a vacuum, but a vacuum abhors a mess. In the absence of air, a droplet of liquid can crash into a smooth surface without splattering, physicists report. The odd phenomenon might be useful for controlling droplet formation in technological processes like inkjet printing.
Splashdown. A drop of ethanol hits a smooth glass at atmospheric pressure (above) and 1/5 atmospheric pressure (below).
CREDIT: Lei Xu et al./The University of Chicago
It seems obvious and inevitable that a fast-moving droplet will splatter when it hits a hard surface. Researchers have studied the distribution of droplet sizes and energies in such splashes, and physicists Lei Xu, Sidney Nagel, and colleagues at the University of Chicago were searching for ways to control those sizes and energies when they discovered something unexpected: By pumping away some of the surrounding air they could eliminate the splatter entirely.
Within a tall vacuum chamber, the researchers released droplets of alcohol onto a dry glass plate from heights ranging from 20 centimeters to 3 meters. They recorded the resulting splashes with a high speed video camera as they varied the pressure in their apparatus, sucking it down as low as one hundredth of atmospheric pressure. The droplets struck the surface with speeds ranging from 2 to 7 meters per second, and for a given speed, the researchers found they could eliminate the splash by lowering the pressure beyond a specific threshold.
The team explains the results with a simple theory. As a drop strikes a surface, liquid begins to spread sideways at supersonic speed, creating a shockwave. The shockwave pushes back on the liquid, and if that force is greater than the internal forces holding the drop together, the shockwave will lift the liquid off the surface and create a splash. Reducing the pressure reduces the force exerted by the shock wave.
Ironically, the theory predicts that a thicker liquid should splash more than a thinner one. The researchers tested this curious prediction by studying the splash made by three types of alcohol with different viscosities. Indeed, the more viscous the alcohol, the lower the pressure needed to prevent splashing, the team reported here this week at a meeting of the American Physical Society.
"It's not uncommon to see a lovely phenomenon, but it is uncommon to get all the factors straight," says Walter Goldburg, an experimenter at the University of Pittsburgh in Pennsylvania. Bulbul Chakraborty, a theoretical physicist at Brandeis University in Waltham, Massachusetts, says the researchers' analysis opens the way to controlling splashing in, for example, spray coating surfaces with various substances.
important puzzle: why do we see a corona form at all? At the substrate surface the liquid momentum points horizontally outward. Without a layer of fluid to push against (such as in the photographs of Edgerton), how does the expanding layer gain any momentum component in the vertical direction?
That is an interesting question...sounds like a potential thesis for a few people out there.
The posting says:
"The results seem to confirm the (perhaps counterintuitive) prediction that more viscous liquids are more likely to splash, not less likely"
While the article says:
"Xu tested water splash as well. Water exhibits the same behavior, but its higher surface tension narrows the range of splash-forming impact velocity and creates a much larger margin for experimental error.
"It's much harder to splash than ethanol," he said."
Is say, this is a classic RTFA
http://www.hairykrishna.f2s.com/droplet.html
"Physics is to math as sex is to masturbation." -R. Feynman
Comment removed based on user account deletion
We invented nuclear bombs before we invented intermittent wipers for cars. Progress is never a smooth line.
This was discussed in Science News (or maybe elsewhere) some time back so I'm working from memory. One of the things reseachers noted was that air was crucial for splashing. It's rather intuitive in a way. All of the momentum is downward, then converted to radially outward. What makes it go up? The leading edge of the droplet is rushing outward. With the right speed and gas pressure, it splashes up like popping the hood of your car while going down the highway. Get rid of the speed or the gas and it will stay low.
The world is made by those who show up for the job.
it looks like all the "splash" is created by the outward spread of the liquid from ground zero, it rushes outwards, but appears to "catch air" presumably because the surface tension / minimum stable raduis has been exceeded, and from that point on it becomes chaotic mixture of small droplets going every which way.
http://slashdot.org/~GuyFawkes/journal
Good job too. Imagine leaving that into the chemist to get developed. "Just the the one set of my 47,000 prints please". And then you get them all back with a 'photography tips' sticker on as you had your thumb over the lens.
You might also want to read the following papers:
A Comparison Analysis of the Greater Carbohydrate and Increased Photosynthetic Element Count of Budweiser Versus the Similar Enzyme Content of Bud Light
Next to medicine and biowarfare, brewing and fermentation technology is a major funding source for microbiology.
Some research suggests that drinking beer may stop your hair from turning grey
And possibly the most expensive PDF's in the world
Vintage computer adverts: http://www.vintageadbrowser.com/computers-and-software-ads
Science at its best. Their explanation passes the three fingers rule. If a complicated subject can be distilled into a written answer that makes sense and can be covered with three fingers, that is elegance. However, don't be confused with answers that makes sense after ingesting three fingers of straight ethanol......
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
Note: This printer has been designed to work in a low atomosphere environment for optimal ink transfers. Reduce air pressure to 17.2 kPa before printing else warrenty will be VOID.
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.
That's exactly the first thing I thought of. And this begs to be simulated.
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.
You pretty much described what is done. The Navier-Stokes equations for compresible and incompressible fluids are used. But in this case air-compression is so low, that incompressiblity could be assumed. All of the difficulty here is tracking the surface and maintaining surface tension. From the equations you can read that the surface tension will depend on two things: pressure jump and the jump of the normal derivative of the fluid velocity. Possibly an artificial surface tension could be added that depended on the change of curvature of the interface surface.
I'm sure it could be done though. Axisymmetric simulation would probably be fine to start off.
Only recently, the preferred approach to date uses a method called the level set method. Here the interface is explcitly tracked. Problems arise here because originally the numerical methods and underlying mathematics that are used weren't set up for changing domains i.e. changing differential equations in the middle of a discrete spacial cell in (a finite element).
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sigamajig...
Can someone explain to me what the significance of this in the real world is? I'm failing to see this (honestly, I'm not trying to be a troll)
I was curious enough about what you said to do some further research. I found the following:
Protein denatures as you beat it up with the whisk Fat globules are dispersed into smaller and smaller droplets as well,,,hey, how would you like to be whipped with sharp slicing pieces of metal?????? All the while, water is swirling and moving creating eddies of air like a sunami in your bowl Sugar is looking for a safe place to land in all the confusion.... End Result: Uncoiled protein (denaturation) surrounds the air bubbles Sugar lands on the denatured protein and holds on for dear life Fat surrounds the sugar, protein and air bubble, trapping the water Now multiply this scene by about 2 zillion K-billion times You have created an interlaced 3-dimesnional net we call a foam (remember our dispersion chart???? Foam is a gas dispersed in a liquid.....air trapped in milk)
So you wouldn't be able to get the milk to turn into whipped cream which turns into butter without the air for the fat, protein, and sugar to cling to. So this is why the milk is shipped in a vacuum.
Full text: http://www2.muw.edu/~jfitzger/page81.html
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.
I don't know about you guys, but this sounds like an effective form a birth control....
Wrong
Strange enough, axisymmetric simulation would probably of little use. Falling drops are one of those phenomena where a completely (or almost completely) symmetrical initial condition leads to a very asymmetrical result. In practice you do not get a circular 'wall' of fluid, but rather a kind of 'crown'. (Google came up with this example). The number of peaks of the crown has been investigated by someone, but I have forgotten who. More about symmetrical conditions leading to asymmetrical results can be found in the book Fearful symmetry.
If a drop of ethanol is dropped on a surface at low pressures (1/5 atmosphere or less), and nobody else is around to see it, does it make a splash?
"In an engine you break the gasoline into millions of pieces and then ignite them in a chamber, making a controlled explosion. You do that continuously in your car," Xu said. "A higher gas pressure might do a better job of breaking the fuel into smaller, more uniform pieces. But determining that would require further experiments more accurately simulating the splash process as it occurs under fuel-combustion conditions," he said.
- Give a man a fire and he's warm for a day, but set him on fire and he's warm for the rest of his life.
"splash-drop" effect.
Bah! Subtle my eye! It's trivial to run your links through an anonymizer to ensure full public access is allowed. Of course, doing this would constitute effort, and it's abundantly clear that /. editors avoid that at all cost...
If a job's not worth doing, it's not worth doing right.
I fear this will collapse into a joke thread, but seriously:
How would the shape of the well-known mushroom cloud change if the detonation occurred in a vaccuum? Would the characteristic double-shockwave be supported by the solids, or does it depend on the atmospheric pressure?
https://app.box.com/WitthoftResume Code: https://github.com/cellocgw
When a drop of ethanol is dropped on a surface...
Because it's a non-Newtonian fluid. More specifically, it's a Bingham plastic. I wouldn't expect any non-Newtonian fluid to behave in a "normal" way. They don't flow like water (plug flow, rather than laminar) and have very funky properties, in general. It's complicated to discuss viscosity of a Bingham plastic, but I think ketchup is another example.
Si la vida me da palo, yo la voy a soportar Si la vida me da palo, yo la voy a espabilar
From here
A Natural Fission Reactor For thirty years it was assumed that the first nuclear chain reaction to occur on Earth was that set up by Fermi in Chicago in 1942. However, it has now been established that a natural reactor operated in a natural uranium deposit in west Africa 1.8 billion years ago. Evidence for this came in an interesting way. Natural uranium from Gabon was exported to France; an examination of the isotopic content showed that the proportion of uranium-235 was slightly lower than normally found This small difference was investigated and traces of the fission products of uranium were found in higher proportions than in normal uranium ore. This suggested that at some time in the geological history of the uranium, some of it had undergone a fission reaction. But how could a chain reaction have been established in natural uranium? The seam of ore, which was being extracted, was unusually rich in uranium-235 (up to 10 per cent). Geological conditions were responsible for accumulating large quantities in a small area. The water of crystallisation of the minerals in the ore might have acted as a moderator. It is now believed that a natural fission chain reaction must have taken place in the ore approximately 1800 million years ago. It may have run for just over 100 years, emitting a thermal power of tens of kilowatts (any greater power would have led to the evaporation of the water required as a moderator). In the course of its lifetime, it would have consumed a similar amount of uranium as a present-day power reactor consumes in a year.