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Science Technology

Phase Change in Fluids Simulated 181

Posted by ScuttleMonkey from the trying-for-real-life-in-a-lab dept.
brendotroy writes "After decades of work by the physics and computer science communities, scientists at the University of Rochester have finally created a mathematical model that will allow scientists to simulate and understand phase changes. This discovery 'could have an impact on everything from decaffeinating coffee to improving fuel cell efficiency in automobiles of the future.'"
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Phase Change in Fluids Simulated More

Phase Change in Fluids Simulated

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  • Decaffeinating coffee? (Score:4, Funny)

    by sconeu ( 64226 ) on Tuesday January 10, 2006 @11:29PM (#14443279) Homepage Journal
    could have an impact on everything from decaffeinating coffee

    So it's going to be used for evil!!!!!

  • Recordable media (Score:3, Funny)

    by saskboy ( 600063 ) on Tuesday January 10, 2006 @11:31PM (#14443283) Homepage Journal
    Perhaps in the future, a swimming pool will hold 10,000 Litres of data by using phase changing properties to store binary computer data.

  • Hardly Fazed (Score:2, Funny)

    by Anonymous Coward
    Since when does it ever get above 32 Fahrenheit in Rochester?

  • Too dense (Score:3, Interesting)

    by texaport ( 600120 ) on Tuesday January 10, 2006 @11:37PM (#14443313)
    Can it show why lakes don't freeze from the bottom up as water approaches 0 Celsius?

    • Re:Too dense (Score:5, Informative)

      by techno-vampire ( 666512 ) on Tuesday January 10, 2006 @11:45PM (#14443347) Homepage
      Can it show why lakes don't freeze from the bottom up as water approaches 0 Celsius?

      No, because that has to do with an entirely different, well-understood phenominum. Unlike most substances, water gets less dense when it gets near its freezing point instead of continuing to get denser. When it freezes, it gets even less dense. (This is caused by something called "hydrogen bonds," but I'm not going to go into that.) Thus, ice is slightly less dense than the water surrounding it, making it float.

    • Not what they're talking about (Score:4, Insightful)

      by MillionthMonkey ( 240664 ) on Wednesday January 11, 2006 @12:32AM (#14443564)
      Can it show why lakes don't freeze from the bottom up as water approaches 0 Celsius?

      Freezing water is an example of a first order phase transition, involving a transfer of latent heat across a clearly defined phase boundary. Algorithms have been able to deal with those for some time (or so I assume). The big breakthrough here is that these guys figured out how to model a second order phase transition (i.e phase transitions in a supercritical fluid) without incurring infinite CPU time.

      Most people are familiar with first order phase transitions (like melting ice or boiling water) but have never seen a second order phase transition. In general first order phase transitions involve a transfer of latent heat, and are noticeably discontinuous- the two phases are easily distinguishable from each other. Second order phase transitions do not involve a latent heat transfer and there is no abrupt discontinuity during the transition, as they occur above the critical temperature and critical pressure, beyond which the liquid and gas phases are indistinguishable.

      The article doesn't explain this at all, but the giveaway here is that the reporter talks about the critical point. [prenhall.com]

    • Re:Too dense (Score:3, Informative)

      by sadtrev ( 61519 )
      Water freezes at the surface of the lake because that's where it's coldest.

      The surface is in contact with cold air that takes away the the water's latent heat. In macroscopic terms this is by evaporation and by conduction across the thermal boundary layer of the air. Changes in the temperature of the ground are more gradual and will slow down freezing by supplying heat to the water at the bottom.

  • The decaf coffee (Score:4, Interesting)

    by Douglas Simmons ( 628988 ) on Tuesday January 10, 2006 @11:38PM (#14443316) Homepage
    I doubt I'm the only one who remembers an article about some breakthrough opening the doors to making decaffinated coffee beans. So far, hasn't happened. Between this and today's other scientific breakthrough of bumblebee flight, are we any closer to a safer and smoother cup of decaf coffee?

    • I don't know why people keep on going about advancements in decaffinated coffee. Everybody in the scientific community knows that God intended for coffee to be caffinated!

    • Makes you wonder what kind of scientist would actually want to work on decaf coffe beans though...

      • Makes you wonder what kind of scientist would actually want to work on decaf coffe beans though...

        A mad scientist, obviously. And quite cranky to boot, I would think.

        But I heard they're trying to insert a gene so it makes opium instead of caffeine. This way you can REALLY have a glass of Coke. That'll rev your engine first thing in the morning ...

    • Re:The decaf coffee (Score:5, Funny)

      by Wizard Drongo ( 712526 ) <wizard_drongo@@@yahoo...co...uk> on Tuesday January 10, 2006 @11:46PM (#14443357)
      WHAT??? Why?? THe whole purpose of coffee is the caffeine. Caffeine is like water; without it, you just can't function. If you want something that doesn't have caffeine it (again; WHY??) drink water. Coffee is a sacred drink. By drinking that horrible stuff that was once coffee but lacks its essence, you're defaming a religion. Please bear in mind the above comments were typed at (local time)04:45hrs after 9 cups of rocketfuel gurana coffee, as I've a presentation to give tomorrow and haven't exactly written it yet. Keynote.app is calling. Laters....
      • I agree. Coffee is vile. If it's not ALSO a caffeine delievery system (i before e.. blast forget it.) it's pointless.

      • Re:The decaf coffee (Score:4, Insightful)

        by gstoddart ( 321705 ) on Wednesday January 11, 2006 @12:32AM (#14443563) Homepage
        WHAT??? Why?? THe whole purpose of coffee is the caffeine. Caffeine is like water; without it, you just can't function.

        Well, sometimes a good cup of coffe is what you want, but if you were to have any now you'd be wide awake for hours.

        Sometimes, it's all about fooling the taste buds without affecting brain chemistry. :-P
      • WHAT??? Why?? THe whole purpose of coffee is the caffeine.

        Just as the whole purpose of sweets is to pump up your glucose! Who cares about taste?
      • Comment removed based on user account deletion
      • Beer is the grossest tasting thing ever. Same with most alcoholic drinks. Any drink, remove the alcohol, I can almost gaurantee it'll taste better. But the alcohol's there for the "special effects" it does to your body. I'm pretty sure many may object to what I just said and what I'm about to say, but I can somewhat understand why people would drink beer (obviously for the alcohol content and not the taste), but I can not find any reason why anyone would drink non-alcoholic beer.
        • Spoken from a Budweiser-Miller-Coors experience, obviously.

          Go try a Fuller's London Porter. It has flavors of coffee and chocolate. And yes, it's beer.

          Coffee flavored beer is called a stout (and the lighter flavored version is a porter). Forget Guinness and Murphy's, they're far too watery. I'm talking a real stout. If you see one, grab a Great Divide Oak Aged Yeti Imperial Stout - it's a drink to behold... But warning, once you travel down the dark path of real stouts, you'll never drink a BMC beer again

          • You know, giving a young person a Stout is a pretty sure way of turning them off of beer forever. I've never met anyone who liked a Stout who wasn't already a beer drinker. Neophytes just can't appreciate the subtle tastes of dark beers. If you give them one all they will taste is the bitter and will be turned into White Wine, or worse Zima, drinkers.
            • Giving a young person a stout is not a sure way of turning them off from beer. I had to cut my teeth on stouts and porters from local breweries because I couldn't stand the flavor of piss-water (Read: Budweiser and their ilk) and I was looking for something to that was a decent, drinkable beer. I wanted to find something I could enjoy with friends while we were playing poker or whatever.

              Amazingly, I've developed a taste for beer in general now, and I can appreciate good pilsners now as well (Budweiser, Co
        • This is of course anecdotal, but it's all I can offer...

          I'm generally a fan of beer in general, and I drink both regular and NA beer. Sometimes I drink beer (or wine or...) to get a buzz, but most times I find myself just wanting to drink something tasty that's not sweet. In fact, I've got half a six pack of Kaliber in the fridge right now, right next to a couple of Leinenkugel's.
      • Please bear in mind the above comments were typed at (local time)04:45hrs after 9 cups of rocketfuel gurana coffee, as I've a presentation to give tomorrow and haven't exactly written it yet.

        ... which is why you are reading /. instead of finishing your work. Ah well, it takes one to know one.

      • Caffeine is a poor substitute for sleep. And if you get enough sleep, you have really weird dreams...

        --LWM
  • Now when they start talking about "phase shifting" on Star Trek, it's not just technobabble - it's science!

  • 2 years from now (Score:3, Funny)

    by Dr. Eggman ( 932300 ) on Tuesday January 10, 2006 @11:50PM (#14443373)
    I see this being apply to video games as the next Lens Flare fad!

  • Phase Change and Complexity (Score:4, Informative)

    by Quirk ( 36086 ) on Tuesday January 10, 2006 @11:51PM (#14443384) Homepage Journal
    The wiki page gives a general introduction to phase change [wikipedia.org]. My limited exposure to phase change has come from trying to fathom the various ideas put forth under the banner of complexity. The Santa Fe Institute [santafe.edu] is the home base for Complexity Theory. A search on the Institutes site turns up a plethora of articles on phase change [google.com]. One of the godfathers of complexity theory, Stuart Kauffman [wikipedia.org] makes many references to the idea of phase change as it applies to his ideas of the origins of life and open, non-equilibrium systems. The International Society for Complexity, Information, and Design (ISCID) [iscid.org] also puts up some interesting material.

    The above gives an introduction to phase change as it is considered in terms of Complexity Theory. Approaching phase change through complexity theory, even for an outsider like myself, gives insight into how far reaching are the results of insight into phase change.

    • Re:Phase Change and Complexity (Score:5, Informative)

      by wass ( 72082 ) on Wednesday January 11, 2006 @12:31AM (#14443558)
      The article says :
      "This is the first time a computer program could simulate a phase transition because the computers would always bog down at what's known as the 'critical slowdown.' We figured out a way to perform a kind of end-run around that critical point slowdown and the results allow us to calculate certain critical point properties for the first time."
      There have been previous methods to look at systems arbitrarily close to the critical point in phase transitions, and the article is misleading when it says this area has been off-limits to computers. I haven't read the actual Physical Review Letters article, but it appears the authors have come up with a novel algorithm, perhaps more ideally suited for fluids, to overcome critical slowdown. But this is not the first such algorithm, and there has been loads of prior computer simulation of phase transitions and critical phenomena to boot.

      For example, in the Ising Model [wolfram.com] or the Potts Model [wolfram.com], one can examine system parameters arbitrarily close to the critical point, in finite time, using a Cluster Algorithm. This page [cam.ac.uk] gives some information on how the cluster algorithm. The page has a java applet graphically depicting the system for a variety of algorithms.

      Just for completeness, here's an Ising model applet [jhu.edu] that I wrote, which doesn't just have a system animation, but allows you to calculate and plot data (specific heat, magnetization, etc) as the system passes through the critical point. This applet uses the Metropolis algorithm for time advancement, hence it is subject to critical slowdown. In that respect, the applet is flawed because close to the critical point I don't generate enough Metropolis iterations to ensure the subsequent frame is sufficiently thermally indepdent from the previous state. However, the cluster algorithm would remove these limitations. This applet has actually been used in graduate physics classes at Johns Hopkins to demonstrate magnetic phase transitions.

      And also for completeness, here's a Potts model applet [jhu.edu], but it doesn't acquire data for plotting like the Ising model. The Potts applet actually uses the Microcanonical ensemble, whereby the energy of the system is conserved, but the Ising applet uses the Canonical ensemble, where the system is in contact with a heat bath at some settable temperature.

      And in case anyone's curious, these applets (except for the first one) are part of the Java Virtual Physics Lab [jhu.edu], which contains a few different physics java simulations I wrote to help with conceptual understanding.

      • Well, the point of their algorithm -- and I haven't read the PRL paper either -- is that it's off-lattice. It's an open question how much off-lattice systems, e.g. real fluids, differ from the lattice models you mention, when it comes to critical behaviour. I think the critical exponents are the same, but other stuff will vary.

        So in that sense, if they've come up with a better simulation algorithm for critical fluids, it's a big deal. At least, it is for chemical engineers, although I grant the physicist
    • "makes many references to the idea of phase change as it applies to his ideas of the origins of life"

      Oh crap, here come the fundies. RUN!
      • I hit preview instead of submit. If I did the link right (very sleepy), that's the paper that introduces the phase transition phenomenon found in Random 3SAT.

        The way I learned it (from Selman), we had computational complexity theory, but no hard instances of problems. The experiment just set out to see if they could generate hard instances. When they did, they found the phase transition, which is well known as where all of the hard instances in 3SAT lie. The phase transition occurs at 4.3 clauses per va
  • /. has talked about face changes before (and we know that spelling's not important here!)

    http://science.slashdot.org/article.pl?sid=05/11/3 0/168239&tid=126&tid=14 [slashdot.org]

  • Slashdotted (Score:5, Informative)

    by Doomedsnowball ( 921841 ) <doomedsnowballs@yahoo.com> on Wednesday January 11, 2006 @12:09AM (#14443475)
    MEDIA CONTACT: Jonathan Sherwood (585) 273-4726, jonathan.sherwood@rochester.edu
    January 6, 2006
    Phase Change in Fluids Finally Simulated After Decades of Effort
    Eldred Chimowitz and Yonathan Shapir

    Everyone knows what happens to water when it boils--everyone, that is, except computers. Modeling the transformation process of matter moving from one phase to another, such as from liquid to gas, has been all but impossible near the critical point. This is due to the increasingly complex way molecules behave as they approach the change from one phase to another. Researchers at the University of Rochester, however, have now created a mathematical model that will allow scientists to simulate and understand phase changes, which could have an impact on everything from decaffeinating coffee to improving fuel cell efficiency in automobiles of the future. The findings have been published in Physical Review Letters.

    "This problem has baffled scientists for decades," says Yonathan Shapir, professor of physics and chemical engineering at the University of Rochester, and co-author of the paper. "This is the first time a computer program could simulate a phase transition because the computers would always bog down at what's known as the 'critical slowdown.' We figured out a way to perform a kind of end-run around that critical point slowdown and the results allow us to calculate certain critical point properties for the first time."

    "Critical slowdown" is a phenomenon that happens as matter moves from one phase to another near the critical point. As molecules in a gas, for instance, are cooled, they lose some of their motion, but are still moving around and bumping into each other. As the temperature drops to where the gas will change into a liquid, the molecules' motion becomes correlated, or connected, across larger and larger distances. That correlation is a bit like deciding where to go to dinner--quick and easy with two people, but takes forever for a group of 20 to take action. The broadening correlation dramatically increases the time it takes for the gas to reach an overall equilibrium, and that directly leads to an increase in computing time required, approaching infinity and bogging down as the gas crosses the point of phase change.

    To illustrate the effect, imagine a perfectly pure and still lake. If you drop a pebble into this lake, its ripples would spread outward, dissipating until the lake had returned to a calm equilibrium again. But, if you were to take this impossibly perfect lake just barely above the critical point and drop your pebble, the ripples would remain as ripples much longer--likely bouncing off the distant shores. This imaginary lake would take seemingly forever to return to its calm equilibrium again.

    The research team of Shapir, Eldred Chimowitz, professor in the Department of Chemical Engineering, and physics graduate student Subhranil De created a novel approach to tackle the phase-change process. They devised a computational model consisting of two separate reservoirs of fluid at equilibrium and near the critical point threshold. One reservoir was slightly more pressurized than its neighbor. The reservoirs were opened to each other and the pressure difference caused the fluids to mix. The team let the simulation run until the entire system reached thermodynamic equilibrium. By watching the rate that equilibrium returned, the team was able to calculate the behavior at the critical point. Their simulation findings match predictions and experimental results, including very precise measurements performed in microgravity on the Space Shuttle.

    "In principle, it's a difficult calculation," says Chimowitz. "Fluid systems require a different class of models than the common lattice models used by researchers who have studied dynamic critical behavior. These different classes give rise to different dynamic critical exponents and we found them, for the first time, in real fluid systems."

    The best known examples of phase changes are perhaps water to ice and

  • Great but... (Score:2, Interesting)

    by Matt Edd ( 884107 )
    This is all fine and dandy but does it help us understand the physics behind it? Long before we (the human race) had any idea what gravity was, we could predict the movement of the planets... but no understanding came of this. Same here. Just because we can write a program to simulate observables doesn't mean we understand them any better. This might be a step in the right direction but it just as easily could lead us away.

    In short... this does nothing for our "understanding" of phase changes.

    • Re:Great but... (Score:3, Insightful)

      by Red Flayer ( 890720 )
      "Long before we (the human race) had any idea what gravity was, we could predict the movement of the planets... but no understanding came of this."

      What about the understanding that the Earth is not the center of the universe? That's a pretty big development, with philosophical as well as physical ramifications.

      Also, we still don't know what gravity is, we just have better mathematical models of it. Ogg the Caveman understood almost as much about gravity itself when he dropped a rock on his foot, as w

    • Re:Great but... (Score:5, Informative)

      by wass ( 72082 ) on Wednesday January 11, 2006 @01:05AM (#14443695)
      In short... this does nothing for our "understanding" of phase changes.

      Wrong, I highly suggest you take a Phase Transitions and Critical Phenomena class if you want to see the utility of methods such as this. As I noted in another post, though, this isn't the first method to allow computer simulations of points arbitrarily close to criticality, there have been other algorithms (eg Cluster algorithm) to allow this too. But every new algorithm to get past critical slowdown is very useful.

      What we've learned in the past several decades in critical phenomena is how parameters change close to the critical point. For example, look up Critical Exponents and Scaling. What is very interesting is that critical exponents are unique to a universality class. So if you are able to take a new system and show that it boils down (no pun intended) to a previously-studied universality class, you can know instantly how various parameters will scale and change as a function of temperature, magnetic field, etc, close to the critical point.

      And to give you an example of this, look at Superconductivity. It was originally discovered by Onnes in 1911, but it took 46 years until the BCS Theory [wikipedia.org] was adequately able to explain how Cooper Pairs form and how resistanceless supercurrent can flow quantum-mechanically. Such a theory is referred to as 'microscopic', meaning it deals with the fundamental physics involved, specifically the electron-phonon-electron interaction and how the Fermi sea is unstable to Pair condensation.

      However - alot of work was done prior to BCS dealing with 'macroscopic' theory, whereby certain laws were able to be formed (eg London equations for classical electrodynamics of a superconductor), we just didn't understand how or why they were valid.

      One such important example is the Ginzburg-Landau theory [wikipedia.org] (Landau won the Nobel Prize decades ago, Ginzburg just got it a couple of years ago), which extends Landau's Theory of 2nd-Order Phase Transitions to use a complex order parameter, which can vary in space. This yields the Ginzburg-Landau equations, which describe VERY WELL the behavior of a superconductor close to the transition point. It was using these equations that Josephson was able to come up with the concept of the Josephson Effect [wikipedia.org] (earning him a Nobel Prize). And Abrikosov was able to come up wit the idea of Type II superconductors and vortices (he also won a Nobel Prize for this work). And after the BCS theory was understood, Gor'kov was able to show that the Ginzburg-Landau equations are a limiting case of the BCS theory close to the critical point.

      However, the point of all this is that it was shown, before the microscopic BCS interactions were understood, scientists were able to do ALOT of things with the Ginzburg-Landau equations. What makes these so great is that they are able to approximate quantum mechanics decently, which the London equations were unable to do. And the best part is that scientists today (myself included) still use Ginzburg-Landau equations to model superconductors. It's just that much easier to use these equations for many interactions than the lower-level BCS theory. But amazingly, these equations were known BEFORE the BCS theory!

      So back to your comment, such study of critical phenomena teaches us a great deal about systems in criticality, even if the methods involved are decoupled from the microscopic physics. Especially if one can determine the universality class of an unknown system. And for very complicated systems, critical exponents will be difficult to determine analytically and must be solved numerically. Hence the importance of simulations and algorithms such as this.

      • And to give you an example of this, look at Superconductivity. It was originally discovered by Onnes in 1911, but it took 46 years until the BCS Theory was adequately able to explain how Cooper Pairs form and how resistanceless supercurrent can flow quantum-mechanically.

        Yup--and the reason that it took 46 years? In part because the researchers involved forgot their first year calculus: they assumed that any function that is infinitely differentiable can be represented by its Taylor series. The assu

      • Re:Great but... (Score:2, Insightful)

        by Matt Edd ( 884107 )
        I know all about this. I know all about critical exponents and scaling and renormalization group theory and superconductivity and BCS theory and... all of that. I am a condensed matter physicist.

        None of that is relevant to my point. I am an experimentalist. I make and measure compounds looking for new physics. If I find a compound with an odd spike in specific heat or a superconducting critical temperature 10K above what is expected then my job only begins. Discovery is one thing (great for chemists

  • What? (Score:3, Insightful)

    by slughead ( 592713 ) on Wednesday January 11, 2006 @12:23AM (#14443528) Homepage Journal
    Decaffinating coffee? Improving fuel economy?

    These are not men!
  • A watched pot never boils. The computers were right all along.

  • Not just plain phase changes (Score:4, Informative)

    by chthonicdaemon ( 670385 ) on Wednesday January 11, 2006 @01:04AM (#14443689) Homepage Journal
    I would like to point out that the article is not about plain phase changes, but rather about phase changes near the critical point [wikipedia.org] , where liquid and gas phases become indistinguishable. Predicting ideal phase change behaviour has been done, but the critical point poses some unique challenges.

  • Could this mean we could see a light emitting fluorescent liquid tube without a 60 (or 50)Hz hum?

    The effects of phase shif flickering are known to be horrible for ergonomics. [ccohs.ca]

  • I want to see a system that can model solid particles, liquids and gases within the same system so that I can finally model biosolids digester gas mixing. So far I have not come across anything that can do it, and so there is no way to tell if a gas mixing system works or not, until you take the digester off-line and shovel out the grit. From what I can tell, they are generally designed using a mixture of experience and guesswork.
  • From that enthusiastic report I gather they will receive the Nobel Prize eventually. I think the man who wrote a groundbreaking chemist program in the 1960's also received the prize some years ago. Wake up, hackers, there is still hope.
  • Is the transition between gas and plasma a phase transition of the same kind? I wonder if this research would help with fusion? I imagine there is a lot more going than a simple phase transition (e.g. gravitational and electromagnetic effects) but it might be one part of the puzzle.
  • Or the press release comes first? I am interested in seeing something more meaty. I have found some related papers but not a specific one. That or just lazy.
  • This is a major deal because there are still LOTS of things that aren't so clear about fluid flow and thermodynamics. For example, one of the things I personally deal with is two-phase flow going through safety relief valves. (ie: you have a liquid and a gas going through the valve). It looks easy. It isn't because it really is "voodoo" as to what actually goes on in that situation. Since there is a pressure drop across the valve, all kinds of weirdness takes place (flashing, etc) and it makes it di

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