Via press release: (Santa Barbara, Calif.) –– Scientists can use cylinders as small as teapots to study the mechanisms involved in powerful hurricanes and other swirling natural phenomena.
The earth’s atmosphere and its molten outer core have one thing in common: Both contain powerful, swirling vortices. While in the atmosphere these vortices include cyclones and hurricanes, in the outer core they are essential for the formation of the earth’s magnetic field. These phenomena in earth’s interior and its atmosphere are both governed by the same natural mechanisms, according to experimental physicists at UC Santa Barbara working with a computation team in the Netherlands.
Using laboratory cylinders from 4 to 40 inches high, the team studied these underlying physical processes. The results are published in the journal Physical Review Letters.
“To study the atmosphere would be too complicated for our purposes,” said Guenter Ahlers, senior author and professor of physics at UCSB. “Physicists like to take one ingredient of a complicated situation and study it in a quantitative way under ideal conditions.” The research team, including first author Stephan Weiss, a postdoctoral fellow at UCSB, filled the laboratory cylinders with water, and heated the water from below and cooled it from above.
Due to that temperature difference, the warm fluid at the bottom plate rose, while the cold fluid at the top sank –– a phenomenon known as convection. In addition, the whole cylinder was rotated around its own axis; this had a strong influence on how the water flowed inside the cylinder. Rotation, such as the earth’s rotation, is a key factor in the development of vortices. The temperature difference between the top and the bottom of the cylinder is another causal factor since it drives the flow in the first place. Finally, the relation of the diameter of the cylinder to the height is also significant.
Ahlers and his team discovered a new unexpected phenomenon that was not known before for turbulent flows like this. When spinning the container slowly enough, no vortices occurred at first. But, at a certain critical rotation speed, the flow structure changed. Vortices then occurred inside the flow and the warm fluid was transported faster from the bottom to the top than at lower rotation rates. “It is remarkable that this point exists,” Ahlers said. “You must rotate at a certain speed to get to this critical point.”
The rotation rate at which the first vortices appeared depended on the relation between the diameter and the height of the cylinder. For wide cylinders that are not very high, this transition appeared at relatively low rotation rates, while for narrow but high cylinders, the cylinder had to rotate relatively fast in order to produce vortices. Further, it was found that vortices do not exist very close to the sidewall of the cylinder. Instead they always stayed a certain distance away from it. That characteristic distance is called the “healing length.”
“You can’t go from nothing to something quickly,” said Ahlers. “The change must occur over a characteristic length. We found that when you slow down to a smaller rotation rate, the healing length increases.”
The authors showed that their experimental findings are in keeping with a theoretical model similar to the one first developed by Vitaly Lazarevich Ginzburg and Lev Landau in the theory of superconductivity. That same model is also applicable to other areas of physics such as pattern formation and critical phenomena. The model explains that the very existence of the transition from the state without vortices to the one with them is due to the presence of the sidewalls of the container. For a sample so wide (relative to its height) that the walls become unimportant, the vortices would start to form even for very slow rotation. The model makes it possible to describe the experimental discoveries, reported in the article, in precise mathematical language.
The other UCSB author is postdoctoral fellow Jin-Qiang Zhong. Additional authors are Richard J. A. M. Stevens and Detlef Lohse from the University of Twente and Herman J. H. Clercx from Eindhoven University of Science and Technology, both in the Netherlands.
Truth is what works. Now make some predictions and we will check how good your model is. However, from my undergrad days, I seem to remember that once you get out of the region of laminar flow, things be come, shall we say, a bit difficult.
OMG!
They have discovered the Coriolis Effect!!!
Quote from start of article
“The earth’s atmosphere and its molten outer core have one thing in common:”
Maybe Inner Core???
Peter
Wow, what deep,intriguing experiments. Takes real “scientists” to come up with yet another hair brain model. Where do all these people come from? I’m sorry, but I seem to have lost faith in the scientific community as a whole.
Reminds me of a Jr. High science experiment I did .-On the Coriolis Effect?!!
Gee and I could’ve applied for a grant. I won’t go into the kid at the next
Table who tried to re-animate a frozen Catfish. Found in ice at a local lake.
Should’ve written a paper on attracting cats…
ShrNfr says:
November 30, 2010 at 9:12 am
well said – but I suppose there should be enough expertise in CFD by now anyway? (computational fluid dynamics).
The tealeaf paradox is used in one of Einsteins most famous papers as the proof of Baers law eg http://en.wikipedia.org/wiki/Baer%27s_law and the meandering river problem.
Albert Einstein, “The Cause of the Formation of Meanders in the Courses of Rivers and of the So-Called Baer’s Law.” Die Naturwissenschaften, 14, 1926
eg http://en.wikipedia.org/wiki/Tea_leaf_paradox
My gosh, we were doing this on the first floor of Felgar Hall at the University of Oklahoma in 1970 when I was a freshman in meteorology.
I don’t know how much this is costing them, but the Pet Tornado is available from Physlink.com for $4.95. “Shake the Pet Tornado clockwise and watch the mini tornado funnel form before your eyes” reads the accompanying copy. “Can you figure out why is it forming? What is the purpose of the fluid and what is the purpose of small particles in the tube?” I don’t know — but I’m sure a team of international scientists can work it out. “Amaze your friends with this amazing desk toy!”
Sounds like fun.
Example http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/fw/gifs/coriolis.mpg
Tempest in a teacup? Take the cylinder walls away and you will have tea in your lap.
Change the speed of spin and perhaps you could eliminate the hurricanes. Help! Research money badly needed.
Milk and two sugars please.
At the risk of sounding too cynical, here’s how this works:
1. Determine that vortices are inadequately understood (a good thing)
2. Launch a research program to understand vortices (a good thing)
3. Finance program by pointing out that vortices are involved in hurricanes, tornadoes and other weather phenomena that are expected to get worse with AGW (a not-so-good thing)
4. Repeat grade-school level experiments which THIS poster performed in grade 6 (blue and red food coloring to show the swirls), claim they’re unexpected and nobody ever noticed before
5. Create a simplified model, sell model to ILM for use in CG used in movies and TV ads, recoup all research program costs
6. Integrate vortex models into Model E, watch in awe as the planet is obliterated by vortices within another few ppm of CO2
7. Exclaim that this is all worse than we thought, and if CO2 emissions don’t stop IMMEDIATELY the entire planet down to the 2 million degree molten core will be torn asunder by vortices. Create HighDef video demonstrating the destruction
8. Sell HighDef video as opening sequence in new climate porn blockbuster Hollywood movie. Earn enough for another home in the tropics. Beachside.
9. Have Vortex Theory and simplified model forcefully inserted into school textbooks, along with a few disclaimers about how most students will never reach adulthood because the Vortices will destroy the planet before then.
10. Determine that all Vortices, globally, are man-made, and before humans walked the Earth there was never a Vortex, ever. Nobody EVER found dinosaur trailer parks torn apart by a tornado, right?
11. When asked by a 7 year old, “aren’t those little winglets on the tips of airplanes because of Vortices?”, rant uncontrollably for hours about how NOBODY ever studied Vortices before you, and that’s all a plot by the Vortex Deniers, funded by Big Calm.
12. Go on anti-depressants after your private emails between you and the NASA guys who first studied Vortexes in the 50s are publicly released. IN spite of the fact that only 4 people downloaded them.
13. End up on late night TV discussing how your enemies in highly funded fossil fuel denier cabals managed to completely destroy you.
14. Found dead in fleabag hotel room in some town nobody ever heard of, a victim of the grand Vortex conspiracy.
http://www.bbc.co.uk/cult/hitchhikers/guide/tea.shtml
Dried Leaves!
Also a vital component of the Infinite Improbability Drive…
Heh heh. “Big Calm.”
Taught in Introductory Fluid Mechanics …but funding hooks necessary:
“Ahlers and his team discovered a new unexpected phenomenon that was not known before for turbulent flows like this. When spinning the container slowly enough, no vortices occurred at first. But, at a certain critical rotation speed, the flow structure changed. Vortices then occurred inside the flow and the warm fluid was transported faster from the bottom to the top than at lower rotation rates. “It is remarkable that this point exists,” Ahlers said. “You must rotate at a certain speed to get to this critical point.””
The Hobbs End Martian.
how improbable was that!
Tea Hee!!!
Here’s a trick I think those doctors in the making can perform to actually test their “new found” phenomenon.
Rotate yourselves around your own central vertical axis, slowly slowly, at first, then faster, faster and faster. And away you go. However, if you don’t attain lift off and go ballistic in five minutes, only stop at your own risk.
Much cheaper ‘an any kind of drugs and with about the same side effects–even the surreal surround sound laughter from the onlookers.
jack morrow said: November 30, 2010 at 9:39 am
“I’m sorry, but I seem to have lost faith in the scientific community as a whole.”
Jack, those of us who are dismayed at the Hockey Team’s perversion of science must resist the temptation to become hardened cynics. The seeds of Climatography’s* own destruction are already sown, and it’s only a matter of time before their half-baked predictions go the way of previous scientific fraud; collapses in ignominy. The pesky planet – and the pesky laws of physics it operates under – cares not that the AGW lobby army is hoping and praying and rooting for for a continuation of the 1975-1998 warm spell.
Our opponents like to claim that we sceptics are somehow anti-science. Nah. It’s BENT scientists we loathe, not the real ones.
*They don’t deserve the ‘ology’; they barely deserve an ‘ography’.
Press Release: “International Team of Scientists Study ‘Flushing Toilet Swirl”
There may be some parallels with turbulent mountain streams that seem to be moving rapidly and the lower wider rivers as they approach the sea which are smoother and seem to be slower. Except higher is slower and lower is faster. Along the way there is friction with the bottom and sides, vortices, and other complicating factors.
Earth isn’t a cylinder – did anyone mention this – so maybe they could move to the space station and work with spheres.
Hey ‘CodeTech’,
That’s not cynical at all: it’s pragmatic foresight based on 20/20 hindsight. The sad part is, that as funny as it is, it’s probably not far off the mark. Good job! 🙂
Reminds me of the end of one fluid dynamics lecture a long while ago where we fetched up singing “irrotational, incompressible, two dimensional fluid flow” to our prof as we were getting bored with the lecture – it goes well to the Cwm Rhondda (“bread of heaven…”) tune. Would’ve thought they’d got it nailed down by now …
In related news, Dr. Ralph Wiggums, Spingfield U., concluded after a 2 year, $5 million dollar research study that indeed his “cat’s breath smells like cat food”.