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Bang But No Splash 252

Posted by Hemos
from the scientific-progress-goes-spash dept.
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."
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Bang But No Splash

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  • Synopsis: (Score:3, Informative)

    by martensitic (747168) on Friday March 25, 2005 @07:38AM (#12044994)
    I do not have access to this item.

    Fascinating. ----- Ut Tensio, Sic Vis

  • Nice! (Score:3, Informative)

    by Anonymous Coward on Friday March 25, 2005 @07:38AM (#12044995)
    Your Free Registration does not grant access to this item:
    Full Text : Cho,Sucking Away the Splatter, ScienceNOW 2005: 4

    • ScienceNOW text (Score:5, Informative)

      by Anonymous Coward on Friday March 25, 2005 @07:56AM (#12045069)
      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.
    • Re:Nice! (Score:2, Insightful)

      by Anonymous Coward
      I guess the conversation was something like:

      <sciencemag> Hi, we'd like to increase our readsership, in the following demographic: nerds
      <osdn> Okay, we can give you the following options:
      <osdn> "Sponsored Link", that'll cost you 100$
      <osdn> "Flash ad", in science section, at 1000$
      <osdb> "Flash ad", front page article, 2000$
      <osdn> "Article in Science Section", it 5000$
      <osdn> or, our most wanted product:
      <osdn> "Article, Front page". 10000 $. Really really a lot o
    • Re:Nice! (Score:4, Insightful)

      by MrP- (45616) <rob@e[ ]emrp.net ['lit' in gap]> on Friday March 25, 2005 @08:25AM (#12045185) Homepage
      this is the second article in 2 days posted on /. that requires payment.. yesterday there was an article that required you to be an AOL member to read it

      wtf is going on??
    • Re:Nice! (Score:5, Funny)

      by Eccles (932) on Friday March 25, 2005 @09:10AM (#12045445) Journal
      Your Free Registration does not grant access to this item:
      Full Text : Cho,Sucking Away the Splatter,


      With a title like that, you would think it's "adult" content they're charging for...
  • Ethanol (Score:5, Funny)

    by KiloByte (825081) on Friday March 25, 2005 @07:39AM (#12044997)
    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.
  • Hmm (Score:4, Funny)

    by iLEZ (594245) on Friday March 25, 2005 @07:41AM (#12045003) Homepage
    " 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..
  • by Anonymous Coward on Friday March 25, 2005 @07:43AM (#12045011)
    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.
  • by ylikone (589264) on Friday March 25, 2005 @07:45AM (#12045019) Homepage
    Click here [uchicago.edu] to see.
  • by Psychic Burrito (611532) on Friday March 25, 2005 @07:46AM (#12045028)
    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.
    • by hey! (33014) on Friday March 25, 2005 @08:01AM (#12045092) Homepage Journal
      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.
    • by efatapo (567889) on Friday March 25, 2005 @08:01AM (#12045093) Homepage
      This doesn't seem that counter-intuitive though...High viscosity liquids have a greater molecular attraction to one another than low viscosity liquids. They would therefore show a resistance to spreading out on the glass. This would give them more solid-like properties and therefore would be more like a ball hitting a wall, where energy is transfered in a rebound. The lower viscosity liquids would not be held tightly together and would therefore spread out easier.

      To test this it seems like you could perform the experiment at higher temperatures. The hypothesis would be that the higher temps overcome the molecular interactions and decrease the viscosity.

      I just looked at the pictures and am a biochemist so take this analysis, like everything else on /., with a grain of salt. But this seems to make sense to me.

      ---
      Daniel Coughlin's Photographs [pbase.com]
      • by Idarubicin (579475) <allsquiet@@@hotmail...com> on Friday March 25, 2005 @10:28AM (#12046120) Journal
        It's one of those things that's utterly obvious--after the experiment is done.

        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.

        • But Jello does look like it's splashing (although not enough to defeat surface tension), and it's very viscous. Putty absorbs impacts, so it's not going to do much. A low viscosity solid would be dry sand, which doesn't splash.

          So the guess probably ought to be that less viscosity means that something will just spread out, medium means that it splashes, and lots means that it goes crown-shaped but no droplets fly off.

          Of course, it's still necessary to do the experiment to determine which, if any, of these
        • Hmm, so will putty splash if the atmospheric pressure is high enough?
        • by bodrell (665409) on Friday March 25, 2005 @02:22PM (#12048213) Journal
          Because it's a non-Newtonian fluid [wikipedia.org]. More specifically, it's a Bingham plastic. [wikipedia.org] 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.
      • This doesn't seem that counter-intuitive though...High viscosity liquids have a greater molecular attraction to one another than low viscosity liquids. They would therefore show a resistance to spreading out on the glass. Zzzzz...

        I wouldn't say it's counter-intuitive at all. Higher viscosity fluids will make a bigger mess when they splash. Therefore, by Murphy's law, it's completely obvious that high viscosity fluids will be more likely to splash.

        -a
    • by Hognoxious (631665) on Friday March 25, 2005 @08:04AM (#12045107) Homepage Journal
      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...
      I'm not sure this is new. A housemate (who worked in a dairy) told me many years ago that milk is transported in vaccuum tankers to avoid it arriving as butter.
      • Yeah, but did the milk SPLASH when it hit the vacuum tanker?

        And did you cry about it subsequently?
      • As I was reading that I was afraid you were going to say so it didn't splash if the tanker got in an accedent.
      • further research (Score:5, Informative)

        by emilng (641557) on Friday March 25, 2005 @10:28AM (#12046122)
        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 [muw.edu]
    • In a sense, it is amazing. It seems like behaviors like these should be "easy" because we've had the tools to investigate macroscopic properties of fluids for a really long time.

      But think of it this way. Your task is to understand the physics of one ping-pong ball verses the physics of many interacting ping-pong balls. Which do you think will be simpler?
    • by MemeRot (80975) on Friday March 25, 2005 @08:34AM (#12045222) Homepage Journal
      We invented nuclear bombs before we invented intermittent wipers for cars. Progress is never a smooth line.
      • by That's Unpossible! (722232) * on Friday March 25, 2005 @09:16AM (#12045507)
        Yes, but they only decided to proceed on the nuclear bombs when they realized dropping intermittent wipers on the Japanese would not end the war.
        • by RobiOne (226066) on Friday March 25, 2005 @10:52AM (#12046376) Homepage Journal
          Yes, but immagine the Japanese's horror if they did drop intermittent wipers all over them!

          They'd think we'd wipe them out.
      • Little factoid -- the guy who invented them died about a month ago today, I think.

      • We invented nuclear bombs before we invented intermittent wipers for cars.

        We had anti-intermittent wipers before the bomb. My father had an 1930's pickup truck with wipers driven by engine vacuum. At rest, the wipers would go like mad. As soon as you started moving, the vacuum would drop off, and the wipers would slow to a crawl just when you need them most. :-)

      • Any for anybody who would like to find out about more random technological inventions that led to great changes in the world, science, and technology, you should check out the Connections Series by James Burke. Truly one of the most fascinating educational programs I've ever seen in my entire life. Even my roommate who could care less about technology and educational documentaries was glued to them.

        You can find torrents for them here [novatina.com].

        I know there was a Connections 2 series floating around on a tracker som

    • I'm not surprised they found these results. After all, fluids of all types tends to behave really differently if you drastically change it from 980 millibars, the standard sea level air pressure. It has all kinds of applications from studying how explosives work to designing high-pressure hydraulic systems for airplanes.
    • by nameer (706715) on Friday March 25, 2005 @10:18AM (#12046040)
      This one has me stumped:

      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?

      • This sounds like something that could be easily explained. When you blow into a balloon, the air inside does not stretch the latex evenly in all directions. By evenly, I mean that the latex is thicker and thinner in some areas than others due to imperfections in manufacturing. When you blow up the balloon, these imperfections aren't accounted for and there are likely to be a few "weakest" areas with some stronger ones around.

        In theory, removing the surrounding air would eliminate or significantly reduce th

      • by fanblade (863089) on Friday March 25, 2005 @12:55PM (#12047465) Journal
        I don't like the other replies to this experiment. They talk about equal distribution of pressures and such, but I think that increasing inside pressure and decreasing outside pressure should create the same effect in that regard. I also don't buy the explanation that it pops "everywhere at once." I would guess that there is always a single starting point for the break. I mean, even if we say that it breaks at TWO points at once, one break probably happens a nanosecond or so before the other. I'm betting that the "everywhere at once" analysis is actually describing a super fast ripple effect that can't be observed in real time.

        The pressure differential between the inside of the balloon and the outside is probably identical in both cases when the balloon pops. So the net force acting on the surface of the ballon at the moment of the pop should be the same. The only difference is the absolute pressure. I think this is the key.

        The pressure in the jar is so low that when the balloon breaks, there is no force pushing inward on the ballon. The net force is basically equal to the force pushing outward. At regular atmospheric pressure there is more force on the inside but also resistance from the outside. I think the outside pressure affects the rubber after the instant of the pop by slowing it down. Maybe this keeps the rubber stable enough to only break into a few pieces.
    • Quote from the Chicago News article "Meanwhile, Nagel and his associates have completed another chapter in their ongoing research program that examines the surprising physics of everyday phenomena."

      Nagel and his associates are quite [lanl.gov] famous for finding interesting physics in things like coffee [uchicago.edu] stains [uchicago.edu] and sand [uchicago.edu] piles and crumpling paper [uchicago.edu]. He taught me quantum while I was an undergrad at U of C, and he was a great teacher, even if I didn't appreciate it at the time.

      It is quite true that there exist interes

    • ...but haven't yet fully understood the properties of athmosphere and vacuum?

      I don't know about you, but I'm pretty sure most of us know the properties of atmosphere in a vaccuum


    • Fluid dynamics is one of the least understood fields of physics and engineering. It is why mega-computers are built and what weather forecasts (and long-range climate prediction) are based on.

      The sky is not falling.
  • (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?
  • by ram4 (636018) <Raphael_Manfredi@pobox.com> on Friday March 25, 2005 @07:53AM (#12045058)
    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?
    • It would be interesting to investigate how superfluids behave.

      It would fight an everlasting battle for truth, justice, and the liquid way!
  • by dAzED1 (33635) on Friday March 25, 2005 @08:12AM (#12045128) Homepage Journal
    Our images illustrate an
    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.

    • 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 slow
  • A single data-point does not confirm. Inline with said theory? Sure.
  • 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
  • Here's the picture (Score:5, Interesting)

    by hairykrishna (740240) on Friday March 25, 2005 @08:24AM (#12045181)
    The pdf link's a little slow and I'm sure people don't want to register for the article so I upped the image onto my website:

    http://www.hairykrishna.f2s.com/droplet.html [f2s.com]

  • 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.

    • Re:Bad link (Score:4, Interesting)

      by Dachannien (617929) on Friday March 25, 2005 @09:57AM (#12045874)
      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.

      • Re:Bad link (Score:3, Insightful)

        by Dun Malg (230075)
        it would be a relatively subtle thing to figure out whether nonsubscribers can read the article or not.

        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...

  • Camera - OT (Score:2, Interesting)

    by FreeLinux (555387)
    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?
  • by jbeaupre (752124) on Friday March 25, 2005 @08:50AM (#12045325)
    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.
    • by Idarubicin (579475) <allsquiet@@@hotmail...com> on Friday March 25, 2005 @10:34AM (#12046190) Journal
      It's rather intuitive in a way. All of the momentum is downward, then converted to radially outward. What makes it go up?

      How about a partially elastic collision with the surface (it bounces)?

      How about collision with the leading edge of the spreading droplet (there is drag on the spreading drop as it extends across the surface--fast liquid building up behind could still splash over that barrier, even in the complete absence of atmosphere)?

      Always be afraid of "intuitive" reasoning in physics when you're dealing with very slow or very fast processes that operate on very small or very large scales. :)

      • by jbeaupre (752124) on Friday March 25, 2005 @11:21AM (#12046643)
        Hey, don't shoot the messenger. I'm just telling you what I remember from the article. As for elastic collision, liquids have no elasticity in the way you are suggesting. Bouncing comes from bulk compression. Fluids, well, flow unless constrained. A droplet isn't constrained so it splats. Except for a miniscule shock propagation wave, you won't get KE->PE->KE of a bounce. But your point about it splashing over itself is a good observation. Sort of creating its own pool then splashing it out. I wonder if they considered it. I apologize for the word intuitive. It's a subjective term.
  • looking at the pix (Score:4, Insightful)

    by GuyFawkes (729054) on Friday March 25, 2005 @08:55AM (#12045361) Homepage Journal
    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.
  • elegant (Score:5, Funny)

    by FLOOBYDUST (737287) on Friday March 25, 2005 @09:16AM (#12045500)
    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......
    • If a complicated subject can be distilled into a written answer that makes sense and can be covered with three fingers, that is elegance.

      I was going to make a comment about writing the answer in Perl code, but then I noticed the "makes sense" part.
      Hey, it can always be done for very large values of finger-width.
      .
      .
      .
      .
      . (I can see *that* comment getting quoted out of context on /.)
  • Simulations? (Score:3, Interesting)

    by geordieboy (515166) on Friday March 25, 2005 @09:28AM (#12045623)
    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.
    • What would be great is to check this phenomenon out with computer simulation.

      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 lo

    • Axisymmetric simulation would probably be fine to start off.

      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 [casburt.com]). The number of peaks of the crown has been investigated by someone, but I have forgotten who. More about

  • 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.
  • Real world.. (Score:3, Insightful)

    by Keamos (857162) <[Keamos] [at] [gmail.com]> on Friday March 25, 2005 @10:18AM (#12046037) Homepage
    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)
    • Re:Real world.. (Score:5, Insightful)

      by jmichaelg (148257) on Friday March 25, 2005 @10:44AM (#12046295) Journal
      We don't know ahead of time what information will turn out to be useful and what will turn out to be arcane so we just gather what knowledge what we can and plod along. It's a strategy that's worked quite well so far.

      Some examples..Transistors arose from some guys shooting the breeze 20-30 years earlier as to how electrons moved around. What they were saying made no sense at all but it paid off big time. A guy sitting in a patent office speculates that light is comprised of particles and uses it to explain why electrons stream out of certain metals. Same guy speculates about what it's like to sit on a photon as it screams along and draws a few conclusions that 35 years later, rock the world. Another guy grows 1000s of peas, counts, by hand, how many of eight different traits show up in subsequent generations and figures out that wrinkled peas require wrinkled parents. Thirty years later, some other guys pick up on that idea and study fruit flys and come up with an arithmetic argument based on percentages that some traits are based on discrete loci. Weird stuff in 1911 that blossomed into billion dollar corporations 70 years later. A pair of mathematically gifted brothers figure out some equations about how fluids move over surfaces. That knowledge sits around for more than a 100 years before a different pair of brothers in a bike shop put the knowledge to an interesting use.

      You just never know what's worth knowing so we gather what we can.

    • From TFA... (Score:5, Informative)

      by Otto (17870) on Friday March 25, 2005 @11:11AM (#12046543) Homepage Journal
      "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.
    • Re:Real world.. (Score:2, Insightful)

      by Nasher (868384)
      Coatings springs to mind. There might be some application in coating surfaces to a high degree of tollerance.
  • Distorted Shape (Score:4, Interesting)

    by LanceTaylor (166490) on Friday March 25, 2005 @10:29AM (#12046129)
    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.
    • Re:Distorted Shape (Score:3, Informative)

      by Jozer99 (693146)
      That was caused by air resistance. A drop falling in pressure such as the atmosphere gets destorted, that is why raindrops have that famous teardrop shape. In the lower pressures, the effect is much less.
      • Re:Distorted Shape (Score:3, Informative)

        by synaptik (125)
        That was caused by air resistance. A drop falling in pressure such as the atmosphere gets destorted, that is why raindrops have that famous teardrop shape. In the lower pressures, the effect is much less.

        Except that raindrops are not teardrop shaped. [fluidmech.net] Thanks for playing.

      • Re:Distorted Shape (Score:4, Interesting)

        by Orp (6583) on Friday March 25, 2005 @05:31PM (#12050135) Homepage
        that is why raindrops have that famous teardrop shape

        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.

  • by williecdog (858695) on Friday March 25, 2005 @10:38AM (#12046229)
    I don't know about you guys, but this sounds like an effective form a birth control....
  • by kramerino (858631) on Friday March 25, 2005 @11:10AM (#12046537)
    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?
  • "splash-drop" effect.
  • 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?
  • by Stankatz (846709)
    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.

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