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.
Isn’t the important bit that they have used detailed experimental observations of an effect many of you are familiar with to build a theoretical model in precise mathematical terms?
math built up without accurate experimental data and not subject to testing/falsification is rubbish (see views on AGW models) but proper math models derived from accurate measurements are to be applauded, surely? Or have I missed something? (whether it is worth the funding I cannot judge, I know next to nothing about fluid dynamics. Just that it can be very important sometimes)
I’d be interested in knowing how they determine rotation rate.
“We found that when you slow down to a smaller rotation rate, the healing length increases.”
Wider cylinders would have faster speed at the edges wouldn’t they. Or perhaps speed is not important but rotation is?
The many of you commentors who have claimed to have done these experiments in days of yore, please explain.
Phlogiston: agree, this experiment is getting at something interesting about how the system is moving energy from one place (hot base) to another (cool top). When the system isn’t rotating, I would bet there are convection cells in the fluid with vertical components but no (or only minor, random) horizontal components. When it rotates, there are shear forces working at the edge of the cylinder (between zero horizontal velocity at the wall, and non-zero velocity in the adjacent fluid). Laminar flow up to some critical velocity and distance from wall; then…? Apparently then there are these vortices, which maybe act to “re-order” the turbulence? And maybe they act as part of the vertical convection cells, somehow increasing the heat flow? I gots no physics here, just some physical intuitions. Help!
May I ask for an off topic help please.
I’m on a new computer and have forgotten the name of the firefox add on that allows me to “bold” “italicise” “backquote” etc my comments. I think it was created by a regular and was available for download here, at Lucias and Steve Macs
Thankyou in advance
Didn’t read all the comments above so likely someone else has observed that these guys are the latest in “Spin Doctors” for AGW
Mike
I find the knee-jerk rejection of the study appalling. For those who say it is some kind of toy or fifth-grade experiment, consider the following:
Historically, finding mathematical descriptions of vortices has been a very difficult problem. The researchers ability to use a theory from superconductivity to describe vortexes in water is indeed a breakthrough. Condescension is unwarranted unless your math is better than that. Mine ain’t …
Are these nodules going to be the new models? I hope not. :o(
Meanwhile, people in the UK as sick to death of Anthropogenic Snowball Warming.
Teaching your grandmother how to suck eggs seems to be the latest phenomenon in the scientific community. Not a day goes by that I don’t hear of some research team somewhere that has just discovered some amazing fact that anyone that’s lived on earth for more than a decade or two accepts as commonplace everyday knowledge. Seriously , Ners need to get out of the office. That’s the biggest problem with climate science they wouldn’t know sunlight if it burnt their vampiric bodies to ash.
Next they’ll be telling us that the earth loses heat faster than first thought because of this new found atmospheric effect and that global warming may not be as bad as they first made out. (/sarc=off)
Mike says: “Didn’t read all the comments above…”
Reading all the prior comments, or even the post itself, seems not to be part of the tribal custom here. Feel free, Mike…
“…so likely someone else has observed that these guys are the latest in “Spin Doctors” for AGW.”
Suspicions confirmed. You didn’t read the post. If you had, you’ve have noted that AGW is not mentioned anywhere in the post, Mike. Your attempt at humor is misplaced, as well as not particularly funny.
Notwithstanding the subject matter, this research and article are not spin.
Interesting that in a containerless wall-less situation, there is no lower limit to the rotational speed required to form a vortex.
GE Smith;
The SH toilet swirl direction is urban legend, apparently. Details of the geometry of the bowl determine the rotation, far overwhelming the planetary Coriolis Effect.
These guys need to work with this guy:
http://www.sciencedaily.com/releases/2010/07/100711163358.htm
The rotating cylinder experiment is described in James Glieck’s excellent 1987 pop-sci best-seller ‘Chaos’, which appears to credit Golub and Swinney with the apparatus design, although Ahlers is also mentioned. The work was generally recognised as a major breakthrough in the understanding of turbulence. If Ahlers’ team has added something new then quite likely it is a significant piece of basic science.
The press release is another matter. By failing to mention prior work and instead immediately linking the research to understanding ‘powerful hurricanes’ I think it gives the wrong impression. I’d be sorry to think that good research like this could only get support by tying itself in some way to ‘climate change’. If anything, the Golub-Swinney experiments show that good basic research deserves support irrespective of political, environmental or social goals.
BrianH: “Interesting that in a containerless wall-less situation, there is no lower limit to the rotational speed required to form a vortex.” Now, that is very cool indeed. I did read the link to the Einstein paper about why tea leaves/rivers cut the way they do, but the physics is still…just…over the horizon for me. The idea that the authors have gotten good mathematics out of this experiment is pretty impressive.
Brian H “Interesting that in a containerless wall-less situation, there is no lower limit to the rotational speed required to form a vortex.”
Slow down – where does the PR say that? Or is it in the paper? Take the rotational speed down to zero and do you still get vortices?
Mods: Please remove my posts @ur momisugly 1 :53 pm and @ur momisugly 2:06pm. Thanks
Willis Eschenbach says:
November 30, 2010 at 3:53 pm
“I find the knee-jerk rejection of the study appalling.”
What is the big deal? Must we bow to the god of science? We’re Americans, for Christ’s sake. We’re having fun!
What we see are two converging explanations that help us understand natural phenomena resulting in climate change. Key to this understanding are the concepts of a `torque’ and what is described as the natural power of `swirling vortices’ as these phenomena relate to the the atmosphere, the oceans, the Earth’s `molten outer core,’ and the formation of Earth’s magnetic field and their effects on climate change.
Adriano Mazzarella (2008) criticized the GCM modelers’ reductionist approach because it failed to account for the many of the factors that can only be understood by taking a holistic approach to global warming. One of these factors is itself just a part but an important larger process that might be describe as a single unit comprised of the `Earth’s rotation/sea temperature.’
Holistically, however, Mazzarella notes that changes in this ‘single unit’ are a result in part of changes in `atmospheric circulation which, like a torque,’ and that alone can cause `the Earth’s rotation to decelerate which, in turn, causes a decrease in sea temperature.’
Similarly, UCSB researchers (the results to be published in the journal Physical Review Letters) seem to be developing a theory of mathematics to help describe this process. The UCSB team `filled the laboratory cylinders with water, and heated the water from below and cooled it from above,’ to better understand the dynamics of atmospheric circulation and `swirling natural phenomena’ observed in nature.
We can apply all of this to Earth science. And, it should not take long before it can be conclusively shown that Trenbreth is never going to find the global warming that he is looking for in the deep recesses of the ocean. The reason is simple: it’s not a ‘travesty’ that we can’t find it. We can’t find it because it’s not there.
No matter how much AGW True Believers may wish otherwise, global cooling is not proof of global warming. Hopefully soon, the mathematics of the UCSB researchers will reveal that given differences in ocean temperature, for example, especially in a real world example where the Earth rotating on its axis with warm water at the bottom, the cold water on the top will sink. The difference in the temperature from top to bottom will of itself be a ‘causal factor’ that drives the flow.
I think we all knew this already. We know it as a simple process of convection. But, let’s hope that the mathematics of it all will help make the AGW government science authoritarians stop acting like persecutors of Galileo.
Re: Brian H says:
November 30, 2010 at 5:34 pm
GE Smith;
The SH toilet swirl direction is urban legend, apparently. Details of the geometry of the bowl determine the rotation, far overwhelming the planetary Coriolis Effect.
The properly rotating bowl was developed by Sir Thomas Crapper (revisionist historians dispute that claim, but the name resides in immortality). The reverse rotating bowl was developed by a typically contrary French inventor named Francois Lew Du Pew. The French bowl failed properly perform its intended function (and hence the expression, “Pew Wee!).
OK, regarding the snark and grade three snark from Frank Lee MeiDere and others.
Getting a true understanding the complex processes of laminar flow in a simple experiment has value. You may think you did this in the third grade but I doubt you or anyone else in your class made any real sense of it. Which is the point, no?
Our world is built upon small advances in “third grade” experimentation. From the basics of thermodynamics (heat flows from hot to cold, oh how K-12!) to the extremely fine domains of magnetic hard drives to hardened fuel cells in space craft.
Having designed a good many hydraulic projects, I understand the point of the study. Laminar flow, which is predictable as opposed to turbulent flow, which is not predictable, and the need to determine when it will change from one to the other, but to try to tie the experiment to atmospheric movements seems foolish.
The atmosphere is on the surface of the planet, and its density varies greatly with elevation. Plus, relative to the thickness of the atmosphere, the surface is, in places, extremely rough. High coefficient of friction, and the coefficient of friction is not at all constant.
I won’t speak for anyone else, but my snark is based on the press release in which two physicists appear to have discovered that if you turn a container with liquid in it slowly, you don’t get a vortex. When you spin it more quickly, you do. Further, that this vortex occurs in the centre, and not near the sides. They also appear to have figured out that the size and shape of the container have an effect — something I’m sure the folks at Tedco and Slinky also worked out when they were making their tornado toys.
If this hasn’t already been looked at in labs then the state of science is in much worse shape than I thought. Science Ouroboros: Vortex Mania
Baa Humbug says:
November 30, 2010 at 3:47 pm (Edit)
May I ask for an off topic help please.
I’m on a new computer and have forgotten the name of the firefox add on that allows me to “bold” “italicise” “backquote” etc my comments. I think it was created by a regular and was available for download here, at Lucias and Steve Macs
Thankyou in advance
greasemonkey
Dang, ofcourse!!! greasemonkey. Thnx Mosh 🙂
It was a cold day, completely snowed in, got to do something or the lab will lose the grant ah heat the water dip the tea bag, apply rotational force, and the rest is history!!
Similar to making paper planes and flying them I guess….