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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.
They're just showing off how many servers they can crush.
- who or what is a Cho
I think it's supposed to be Chode Boy.
how 'bout I give you the finger....and you give me my phone call.
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.
A single data-point does not confirm. Inline with said theory? Sure.
Were that I say, pancakes?
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.
The link given is to a login page, not to an article. It would be really nice if the editors caught these and filtered them out before posting.
The pictures were captured by the Phantom V7 camera at a rate of 47,000fps.
I wonder how long it will take to get a digital equivalent of this camera?
A bit faster than my Canon 10D! I want one!
Kevin
"It's not the cough that carries you off, it's the coffin they carry you off in" O. Nash
As any geek will tell you... size ALWAYS matters! Even if it's only related to the hardware you recently bought.
Cliff Claven
K.E.G. Party Chairman
Founding Leader of: Koncerned for Egalitarin Governance
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
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
This is why you must never, ever, ever attempt to RTFA. It's just easier this way :)
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
With that headline, I was secretly hoping they had photos of a tiny fireball. But nooooo.
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.
I'm not a physicist, but even I can (seemingly) work this stuff out from first principles: a rubber ball bounces more than a brick because it's a soft body that can be bent, distorted, and recoiled by the forces involved in hitting the ground. Likewise, a more viscous liquid can hold in its forces more than a "lesser" liquid, and its shape will bend and distort as the forces (and fluid) push around inside it. Nothing counter-intuitive there to me.
Now, knowing something intuitively and validating it scientifically are two different things, and I (at least) wasn't aware that some liquids don't bounce, so I welcome this research of course. But I hope it leads to something a little more groundbreaking than that ;)
I'd also like to know if this ethanol is REALLY not bouncing all of a sudden, or if it's just bouncing less so that it becomes undetectable.
WOW!
Where are the pictures?
NEAT!
*gets back to work*
Please stop stalking me, bro.
Have a look at the PDF:
This equation predicts another non-intuitive result: a more viscous liquid splashes more easily than a less viscous one.
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).
______________________________________________
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....
That reminds me of an experiment where they dropped thousands of ping pong balls down a slope to simulate an avalanche:
http://www.sciencenetlinks.org/sci_update.cfm?Doc
Consider dropping water through atmosphere. It can from a cup of water off a roof or even standing on a chair.
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.
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....
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.
Had to make up all the results in the end, just so I'd have something to report.
Heh, heh.. Been there, done that!
TTYL, Dan Rather
I don't need no instructions to know how to rock!!!!
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.
I wonder what kind of splash a web server makes when it hits bottom? But yes, this article is a bit over the top. You can have good news, interesting news or slashdot news. Take your pick, but you can't mix and match.
The world according to SComps
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
Because reductionism is the only thing that works.
But beyond that, pretty much the definition of "fundamental" insures that knowing the actions of individual component particles is more fundamental than knowing the actions of large numbers of component particles, because the latter is a subset of the former: the rules specific to higher numbers of particles can be written in terms of those governing individual particles, but not always the other way around.
Wholism had its shot for the first 95% of human history. The last 5% has worked orders of magnitude better in much less time.
When a drop of ethanol is dropped on a surface...
If you look at the pictures, the splash droplets are actually taking off, much like a plane, because of the air drag (they're moving fast sideways, some air gets underneath, therefore they take off).
If there's no (or little) air, the lift-off force is smaller, therefore they're less likely to take off.
That's pretty much like a high-speed boat (or car) tipping over because of the very high speed - if there wasn't air, it wouldn't tip over.
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.
Si la vida me da palo, yo la voy a soportar Si la vida me da palo, yo la voy a espabilar
My guess is the bubbles were from an existing thin crack leak, and you exacerbated it by playing with vaccuum.
If you heat glassware with no liquid, it gets hair-fine cracks in it, and will shatter if you touch the (apparently solid) body. Glass is an amorphous solid similar to plastics.
I think the point was that substances can behave in unexpected ways. Water does not appreciably change its viscosity when cooled to near its freezing point, yet ethanol does thicken before it freezes.
A really neat experiment is to melt some chunks of solid sulfur and slowly raise the temperature of the melt. It starts out as a slightly viscous straw-colored liquid when the sulfur molecules are little donuts of S8. Then, as the temperature rises, the donuts break apart and reattach to each other, making long strands which become entangled, and the liquid darkens and thickens.
What does this have to do with Ethanol splashes? Not much, but it's interesting nonetheless.
Yea, except that increasing the pressure on the inside is the same as decreasing the pressure on the outside. The imperfections are still there and in either case you're simply creating positive pressure inside the balloon.
I used perl years ago, and it's expressive, but I personally went the VB
route myself.
Where's the part of your theory where you explain why removing the air from the chamber makes the splash go away?
Patrick Doyle
I mod down every jackass who puts his moderation policy in his sig. Oh, wait a sec....
As I understand it, the "trunk" of the mushroom cloud is caused by the in-rushing shockwave.
1. Bomb goes off and drives air away from explosion point in a hemispherical fashion (for a ground burst).
2. Air rushes back from all directions, but mostly at ground level where air pressure is highest.
3. This "squirts" the smoke and debris upward till either the air gets thinner or the in-rushing air stops. This creates the "stem".
4. At this point, the smoke and debris start spreading outward, creating the mushroom cap.
By the way - such clouds can be created by any large enough explosion, it doesn't have to be nuclear.
Clear, Dark Skies