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.
CodeTech says:
November 30, 2010 at 10:29 am
At the risk of sounding too cynical, here’s how this works:……….
Very good.
I enjoyed that.
And if you change the rotation you don’t need any temperature difference at all.
http://einstein.atmos.colostate.edu/~mcnoldy/spintank/
That’s a vortex above the teacup, not a vortice.
Regards,
Mike
grammar n*zi
I seem to recall that James Bond prefered his martinis a certain way – shaken, not stirred. The next movie will probably have him order his martini swirled, not shaken or stirred.
I’m not for sure what is new here, but I suspect it’s the transition point that relates to formalisms in superconductivity. Changes in stability and their explanations are an important part of hydrodynamics and thermodynamics. I note that very little if anything gets into Phys Rev Letters that is not of high interest and novelty, albeit in fields of sometime limited interest.
The point is that immediate dismissal of someone’s work without understanding what has been done or its significance does not serve the skeptic community well. Some of the replies here have the character of knee-slapping yokels motivated by poking at anything that comes along. Besides there is nothing in the work that immediately relates to AGW pro or con, simply a simple observation, likely correct, that may have been missed, despite the simplicity of the system. Most good discoveries turn out to be simple and obvious when explained.
So far, the great majority of the commenters in this thread are dismissing this article because haven’t a clue as to the actual science involved, possibly either because the press release is written for general readership or because they have insufficient background in science to see beyond the prose therein. I’ve met Guenter Ahlers and I can assure you that he has a first class intellect. I saw him give a paper at an SAACS conference in Redlands, CA. His paper was head and shoulders above anything else presented. I once interviewed for a job in Riverside. When I was told that the other candidate was Dr. Ahlers, I advised the interviewer to hire him if they possibly could.
Guenter Ahlers received his BA degree in chemistry from UC Riverside in 1958 and a PhD in physical chemistry from UC Berkely in 1963. In 1963 he became a Member of Technical Staff at Bell Laboratories in Murray Hill, NJ. There he worked on critical phenomena near the lambda point in liquid helium and near magnetic phase transition, and on superfluid hydrodynamics. In 1970 he began research on Rayleigh-Bénard convection in liquid helium that led to the experimental observation of chaos in a fluid-mechanical system. In 1979 Ahlers moved to UC Santa Barbara, where he studied pattern formation in convection and Taylor-vortex flow, and turbulent Rayleigh-Bénard convection. He and his co-workers published about 270 papers in the Journal of Fluid Mechanics, Physics of Fluids, Physical Review A, B, and E, Physical Review Letters, and elsewhere. Ahlers became a Fellow of the APS in 1971 and of the AAAS in 1990. He received the IUPAP Fritz London Memorial Award in low-temperature physics in 1978, the Alexander von Humboldt Senior US Scientist Award in 1989, and the APS fluid-dynamics prize in 2007. In 1998 he was a Guggenheim Fellow. He was elected to the National Academy of Sciences in 1982 and became a Fellow of the American Academy of Arts and Sciences in 2004.
See the paper at: http://physics.aps.org/articles/v2/74
I really don’t understand the snark and jeers in the comments section about this example of basic investigative physics. Please explain and expound on why it is not valid and deserves ridicule.
Google only finds the term ‘healing length’ in association with Bose condensate and liquid helium (ie superfluids).
Is it also room temperature concept?
Wow, I have never seen such a collection of lame half cocked and condescending comments on WUWT, as I am reading now. Obviously, no one bothered to find out what the researchers are reporting. sheeesh!
lgl says:
November 30, 2010 at 12:29 pm
And if you change the rotation you don’t need any temperature difference at all.
http://einstein.atmos.colostate.edu/~mcnoldy/spintank/
That barotropic instability looks suspiciously like visual features on Jupiter.
The same lead researcher ten years ago…
{Head stuck in a Gym toilet getting a “Swirly” by field hockey team member}
“I wonder why the water spins in a circle like that”.
Gotta buy some stock in Lava Lamps Inc!
Well, there’s this, of course:
It’s hard to actually explain why there are such jeers at what is a grade three physics experiment. When you turn the cylinder slowly, you don’t get a vortex. When you spin it faster, you do. I mean, seriously? You can buy “tornado” toys that use this principle.
The funding that will go into this would be far better spent on science classes at the grade school level — not that they’d be doing “experiments” like this, however, since they’d be deemed too elementary.
One thing we do know — these guys are not smarter than a fifth grader.
Re: jorgekafkazar says:
November 30, 2010 at 12:49 pm
“I’ve met Guenter Ahlers and I can assure you that he has a first class intellect. ”
Toilet bowl swirl has long attracted “first class intellects”, beginning with plumbing legend, Sir Thomas Crapper.
@jorge
‘So far, the great majority of the commenters in this thread are dismissing this article because haven’t a clue as to the actual science involved, possibly either because the press release is written for general readership or because they have insufficient background in science to see beyond the prose therein. I’ve met Guenter Ahlers and I can assure you that he has a first class intellect. I saw him give a paper at an SAACS conference in Redlands, CA. His paper was head and shoulders above anything else presented. I once interviewed for a job in Riverside. When I was told that the other candidate was Dr. Ahlers, I advised the interviewer to hire him if they possibly could.’
So essentially you fire all cannons trying to sink everyone by trying to impress a bunch of skeptics with the bestest of strategy by appealing to authority or as google apparently would have it, argumentum asinum oscula. :p
Sorry! Coriolis effect does not work at these scales.
Dr. Ahlers might add the sun to his targeted swirling bodies. It appears to respond similarly, but its descent from patterned swirling to chaos is ill understood. But the recurrence to pattern along with the periodic nature of sunspot might make for an interesting subject to gain further knowledge.
@ur momisugly Peter Walsh:
Peter Walsh says:
November 30, 2010 at 9:24 am
Quote from start of article
“The earth’s atmosphere and its molten outer core have one thing in common:”
Maybe Inner Core???
Peter, the reason they specifically mentioned the “outer core” as being molten is because from seismic data, we know that S(hear)-waves do not pass through liquids or molten material. Seismic ray paths that pass through the outer core show no S-wave component.
Peter Walsh says:
November 30, 2010 at 9:24 am
Quote from start of article
“The earth’s atmosphere and its molten outer core have one thing in common:”
Maybe Inner Core???
Peter
Peter: The reason the authors specifically mentioned the “outer core” as being molten is because we know that S(hear)-waves do not pass through molten or liquid substances. Seismic waves that pass through the outer core and reflect off the inner core and are recorded at the surface show no S-wave component. Therefore the conclusion is that the outer core is molten or a liquid.
@ur momisugly Peter Walsh:
Peter Walsh says:
November 30, 2010 at 9:24 am
Quote from start of article
“The earth’s atmosphere and its molten outer core have one thing in
in common”
Maybe Inner Core???
Peter, the reason they specifically mentioned the “outer core” as being molten is because from seismic data, we know that S(hear)-waves do not pass through liquids or molten material. Seismic ray paths that pass through the outer core show no S-wave component.
This is not the Coriolis effect, that is linear, this is nonlinear. A classic Hopf bifurcation laminar-turbulent transition. With increasing rotation speed the system is gradually driven away from equilibrium. At a certain disequilibrium point, nonlinear pattern formation breaks out. The increase in warm fluid transport at the critical transition point could possibly tie in with (and give support to) Willis’ Constructal Law (systems converge to maximise flow of something) despite the hard time his theory was given on a recent thread here. The “boundary forcing” referred to is well known in for instance Rayleigh-Benard pattern formation convection in liquid helium.
Andy J says:
November 30, 2010 at 12:39 pm
jorgekafkazar says:
November 30, 2010 at 12:49 pm
David Walton says:
November 30, 2010 at 12:53 pm
===================================
Thanks for pointing out that many of the points being made are not on point, which brings me to my point ;o)
I wasn’t quite sure what to make of this post because it seems so simple – I too had to do some swirly experiments back in the day – and yet there seemed to be something I was missing. I usually like to make a giggler comment on a post like this but something kept niggling at the back of by brain.
I’ve been checking in on the comments from time to time and each time I come back, I keep scrunching up my eyes and trying to visualize the boundries of a vortex before and after it forms to where we can see it. I intend to check back a few more times until hopefully, I “get it.”
Anyhow, your comments were the “tipping point” (fair use of that, eh?) to keep on pondering instead of posting something about funding creamer swirls in coffee.
Billy Liar
Yet still they wonder why.
Tell you what… for those 2 people in the entire world who think my post was mocking the study of vortices, check the first two points… they both say “(a good thing)”.
It is truly unfortunate that with the state of Science lately, the remaining 12 points of my post would be unsurprising, if they were to occur.
In fact, the study of vortices is serious business, and has innumerable real-world benefits (including those winglets I mentioned, they actually reduce fuel use or increase aircraft range, depending on your perspective).
Further understanding of physical processes is always a good thing. Personally, I love study of real-world, and while I’m fine with models I think we’ve all seen the “worst case” scenario of simplified model usage taken to ridiculous extremes.
Well I didn’t see that they said anywhere that they have yet discovered that when you flush the toilet in the southern hemisphere, that it rotates, in the opposite direction from the northern hemisphere.
I can see the need for a research grant to examine toilet flushings from pole to pole to find out what the blazes happens at the equatorial regions, when the flush stops goping one way, and starts going the other way. Perhaps that’s why they don’t have flush toilets in some parts of Africa; because the things simply will not rotate in either direction.