Recipe for Making Symetrical Holes in Water

scottZed writes "Danish researchers found a simple way to make curiously shaped air holes in a bucket of water. Simply rig the bucket to have a spinning plate at the bottom, and depending on the speed, you can get an ellipse, three-sided star, square, pentagon, or hexagon. The effect may help explain such shapes seen in atmospheric disturbances on Earth and other planets. One practical use: really trippy washing machines."

Comments

Sloppy reporting.

[Anonymous Coward]

TFA:

Bizarre geometric shapes that appear at the centre of swirling vortices in planetary atmospheres might be explained by a simple experiment with a bucket of water.

The bucket explains nothing - it might replcicate atmospheric conditions to the point where it will be a good model to aid in understanding atmosphereic conditions.

This from a publication with the byline "the best in science journalism"

Bah!

Re:Sloppy reporting.

[MrShaggy]

Quoted from the article .." These natural structures have never been fully explained. Could they be produced by the effect observed by the Danish team? "I expect that similar conditions might apply in these atmospheric flows," says Bohr. But he admits that at this stage he doesn't understand the pattern-forming process well enough to be sure of the comparison.

Swinney, meanwhile, thinks that the process is unlikely to apply to large-scale flows such as that on Saturn, but might be relevant to smaller-scale phenomena such as tornadoes."

Seems that they realize that this is but baby steps, and there needs to be much more work done.

Re:Sloppy reporting.

[i_should_be_working]

It's how you decipher something that makes it an explanation.

Einstein's equations of general relativity don't really explain anything unless you understand the math. To anyone else, they're just kooky looking symbols. To many people these may just be buckets with spinning water in them. To these researchers they may turn out to be explanations.

Re:Sloppy reporting.

[m0nstr42]

Seems that they realize that this is but baby steps, and there needs to be much more work done.

Amen. I'm getting sick of people reading a /. summary of a summary of someone's legitimate results and deciding then and there that the original research (whose message is now 2x re-interpreted by the successive authors) is crap. These people do this for a living; many hold tenure positions at prestigious research institutions that are reserved for the brightest in their fields. Most of their really significant results appear in peer-reviewed publications. They're probably slightly more qualified to decide what is significant in their fields than you are.

Popular media tends to mangle the crap out of stories in an effort to make it accessible to a wide variety of people. This is necessary for the sharing of information and the generation of public interest in scientific progress. If you're semi-intelligent and a particular story catches your eye, you should know enough to read between the lines a little bit. If you want to make any claims regarding validity, you need to find the original publications and make a slightly better assessment than a half-page web story can provide you with.

Re:Sloppy reporting.

[iamlucky13]

To expand on the parent, the effect is called "similitude." The Reynolds number is a dimensionless number that involves the velocity of flow, the size of any defining flow feature (like pipe diameter), and the viscosity of the fluid. These are the primary factors that effect how a fluid flow will act on a larger scale.

Unfortunately, this sort of thing doesn't work very well on a small portion of a system. Instead, computational fluid dynamics involves breaking the flow up into discrete elements, figuring out what each element should be doing (typically according to the equations used on larger or simpler systems), then figuring out how that effects the element next to it. Then you do the whole thing over again with new initial conditions defined by how all the elements effected each other. Then you do it once more. Then you keep doing it over and over until the difference between subsequent iterations gets small enough to make you happy (assuming you didn't screw up and it diverges). The ability to do this with a computer definitely opened new gateways for engineering with fluids, but it's still only an approximation, and there are some effects they have trouble figuring out. I don't think anyone can really appreciate the difficulty of some of the common problems like long-term or highly accurate weather or climate predictions until they've tried to solve a finite element problem involving just 4 elements (especially if you have complicating factors like heat transfer). Then you look up at the sky and multiply the difficulty by several billion or so.

A couple of my friends in school worked summer research projects with one of our physics professors looking at a related effect known as Stewartson layers (basically, the shear rate of a fluid isn't actually linear across a flow in which velocity changes with position, like we usually model it as...sometimes the flow forms in "sheets"). I don't know all the details, but like the effect in the article, this one isn't well understood.

Interesting

[Anonymous Coward]

Aliens obviously use the plate to transmit geometrical patterns in an effort to contact us. This proves it beyond all doubt.

Re:Interesting

[jginspace]

Aliens obviously use the plate to transmit geometrical patterns in an effort to contact us.

I doubt they'd resort to those means. I'm sure they know that Skype has just introduced free calls to land lines and mobiles in the US and Canada until the end of the year: http://www.skype.com/company/news/2006/skype_freec alling.html

Just a resonance?

[mangu]

Well, if you have waves in the bucket, and the circumference of the hole is a multiple of that wavelength, then it's very natural that this phenomenon should happen.

I'm curious about the researcher's name, Tomas Bohr, any relation to Niels?

Re:Just a resonance?

[pheede]

Yes, he's the grandson of Niels Bohr. His two cousins, Henrik and Jakob Bohr, are also professors at the Department of Physics at the Technical University of Denmark.

Re:Just a resonance?

[ZombieWomble]

Well, if you have waves in the bucket, and the circumference of the hole is a multiple of that wavelength, then it's very natural that this phenomenon should happen.

In that situation, there would be perfect axial symmetry as these wavelengths would be identical in all directions, giving a fixed circular standing wave pattern once the flow stabilised (given a symmetric bucket, obviously). However, in this case, we have a breakdown in axial symmetry, and instead have slowly rotating geometric shapes instead.

Re:Just a resonance?

[binarybum]

yes and don't forget that Ima Bohr, Whadda Bohr, and Yura Bohr all founded the Institute of Neutrino Generation - Commonly referred to as Bohr-ING.

Interesting Effect

[Anonymous Coward]

It looks like the end result of system resonance set up between the harmonics and the properties of water. It would be cool to artificially vary the viscosity of the water with polymers, or add salts to increase specific gravity to note the affect on the pattern properties. OK, some of you are thinking, this guy is a nut but it just proves how never ending the learning process is as it relates to even the simplest things observed in nature. I like it.

TFSummary says "Three-sided star..."

[Khyber]

I say "Triangle"

Practical

[suv4x4]

One practical use: really trippy washing machines

practical

adj 1: concerned with actual use or practice; 2: guided by practical experience and observation rather than theory; 3: being actually such in almost every respect; 4: having or put to a practical purpose or use;

Pedantic

[Anonymous Coward]

pedantic

adj 1: Like a pedant, overly concerned with formal rules and trivial points of learning; 2: Being showy of one's knowledge, often in a boring manner; 3: Often used to describe a person who emphasizes their knowledge through the use of vocabulary; 4: Being finicky or picky with language.

Re:Pedantic

[suv4x4]

pedantic

adj 1: Like a pedant, overly concerned with formal rules and trivial points of learning; 2: Being showy of one's knowledge, often in a boring manner; 3: Often used to describe a person who emphasizes their knowledge through the use of vocabulary; 4: Being finicky or picky with language.

joke: n. 1. Something said or done to evoke laughter or amusement, especially an amusing story with a punch line. 2. A mischievous trick; a prank. 3. An amusing or ludicrous incident or situation.

Re:Wow

[fish waffle]

seriously, what if in the ocean the waterflow is spinning very hard itself under certain conditions, wouldn't that be a possible explanation for the disappearances in the Bermuda Triangle?

Yes, that's right. A suitably airplane-shaped hole would indeed allow an airplane to fall to the bottom of the ocean without getting wet, nicely and logically accounting for its sudden and complete disappearance. Similarly, holes isomorphic to boats and drowning people would account for those inexplicable losses.

Oh, wait, Bermuda triangle---you probably meant a triangular hole. No, sorry, that's just stupid.

Re:Wow

[Decaff]

But seriously, what if in the ocean the waterflow is spinning very hard itself under certain conditions, wouldn't that be a possible explanation for the disappearances in the Bermuda Triangle?

You don't need an explanation for the disappearances in the Bermuda Triangle, at least no special explanation. The disappearances there occur at no greater frequency per unit of shipping or flight than anywhere else in the world.

Re:Instability?

[NeutronCowboy]

You're confusing randomness with chaos theory. Randomness is essentially us saying "We might know the principles at work, but it's too complicated for us to make an accurate prediction on what is exactly going to happen." Brownian motion is one such example. We have a good idea on the physics behind it, but the huge number of interactions that take place mean that we can only predict the behavior of the entire system, not of single particles in it. Furthermore, single particles do not show a propensity to do anything in particular. You won't find random particles moving in circles, for example.

Chaos theory deals with systems where we can calculate effects on single objects in the system, and where these objects exhibit non-random patterns. You mentioned fractals already (although strictly speaking, that's defined as a complex system rather than a chaotic one), and population growth patterns are another.

Photos and video

[Falkkin]

Some better photos can be found here, along with a video. Unfortunately the video seems to show the vortex from its side rather than the top. Pretty cool though!

http://dcwww.camp.dtu.dk/~tbohr/RotatingPolygon/