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14 Jul 2024 22:16:07 EDT (-0400)
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From: Bald Eagle
Subject: Petaled / polygonal vortex
Date: 27 May 2024 18:35:00
Message: <web.66550a8f5e97689f1f9dae3025979125@news.povray.org>
So, I was just stirring some boiling water to make some pasta, and the vortex
was actually 5-sided, with the water from the preceding side apparently sliding
underneath the next.

Things like this are becoming increasingly hard to research, as web searches
aren't what they used to be.  Like finding "troposkein".

Might anyone know of a mention of this in the mathematical, geometric, or
physical science literature?   Seems like it would be a cool 3D curve to make -
once I have the requisite round tuits.

- BE


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From: ingo
Subject: Re: Petaled / polygonal vortex
Date: 28 May 2024 01:55:00
Message: <web.665570ecea664b2217bac71e8ffb8ce3@news.povray.org>
"Bald Eagle" <cre### [at] netscapenet> wrote:

> Things like this are becoming increasingly hard to research, as web searches
> aren't what they used to be.


Well, if it is physics, always ask Feynman. I found
https://www.feynmanlectures.caltech.edu/II_41.html (The flow of wet water) I did
not read it, but it has pretty pictures with vortex and "why the flow breaks up
in bands".

ingo


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From: Cousin Ricky
Subject: Re: Petaled / polygonal vortex
Date: 28 May 2024 11:34:41
Message: <6655f991$1@news.povray.org>
On 2024-05-28 01:51 (-4), ingo wrote:
> 
> Well, if it is physics, always ask Feynman. I found
> https://www.feynmanlectures.caltech.edu/II_41.html (The flow of wet water) I did
> not read it, but it has pretty pictures with vortex and "why the flow breaks up
> in bands".

One nitpick, which is actually irrelevant to the topic: glass is no
longer considered a liquid.  This claim was based on an old definition
of "solid" that required a regular crystalline lattice.  Glass is now
considered an "amorphous solid."

Contrary to what you may have heard, glass does not flow; if it did,
large telescopes would fall permanently out of focus.  The reason some
medieval windows are thicker at the bottom is that glass making
technology was not as precise in those days, and the builders who
installed the subsequently uneven panes were not stupid.


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From: kurtz le pirate
Subject: Re: Petaled / polygonal vortex
Date: 28 May 2024 12:37:30
Message: <6656084a$1@news.povray.org>
On 28/05/2024 00:34, Bald Eagle wrote:
> So, I was just stirring some boiling water to make some pasta, and the vortex
> was actually 5-sided, with the water from the preceding side apparently sliding
> underneath the next.


It reminds me of the hexagonal structure at Saturn's pole :
<https://science.nasa.gov/mission/cassini/science/saturn/hexagon-in-motion/>




-- 
Kurtz le pirate
Compagnie de la Banquise


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From: Bald Eagle
Subject: Re: Petaled / polygonal vortex
Date: 28 May 2024 14:30:00
Message: <web.66562197ea664b22e21e5c0b25979125@news.povray.org>
Cousin Ricky <ric### [at] yahoocom> wrote:

> Contrary to what you may have heard, glass does not flow;

I'm inclined to argue from observation (anecdotal evidence) that it does.  vide
infra *

> if it did,
> large telescopes would fall permanently out of focus.

But there are many types of glass, and some may flow orders of magnitude slower
than others.

> The reason some
> medieval windows are thicker at the bottom is that glass making
> technology was not as precise in those days, and the builders who
> installed the subsequently uneven panes were not stupid.

Interesting, but not in and of itself proof that glass does not flow.

* I have driven past old industrial buildings in, IIRC, northern New Jersey
(probably ironbound Newark) and the glass panes in the windows had flowed down
so much that there were holes opened up and the glass all collected and bunched
up at the bottom of the hole.

Now unless there were some amazing heat (I saw no evidence of fire damage - no
soot marks, frames still intact) I don't see how that would have happened unless
glass does indeed flow.

It would be interesting to put a weight on a pane of flint glass supported on
either end by sawhorses, and see what happened over a long period of time.

-BW


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From: MichaelJF
Subject: Re: Petaled / polygonal vortex
Date: 28 May 2024 15:04:03
Message: <66562aa3$1@news.povray.org>
Am 28.05.2024 um 00:34 schrieb Bald Eagle:
> So, I was just stirring some boiling water to make some pasta, and the vortex
> was actually 5-sided, with the water from the preceding side apparently sliding
> underneath the next.
> 
> Things like this are becoming increasingly hard to research, as web searches
> aren't what they used to be.  Like finding "troposkein".
> 
> Might anyone know of a mention of this in the mathematical, geometric, or
> physical science literature?   Seems like it would be a cool 3D curve to make -
> once I have the requisite round tuits.
> 
> - BE
> 
> I found some papers may be related to this question. But I'm far away 
from a deeper insight in this matter. First:

https://journals.aps.org/prfluids/pdf/10.1103/PhysRevFluids.4.100507

But as I understand it, the authors have only speculations about the 
reasons and the setting seems to be not exactly the same.

May be a related phenomenon:
https://arxiv.org/pdf/physics/0511251#:~:text=In%20a%20flow%20driven%20by,from%20that%20of%20the%20plate.

In the following paper the authors try a numerical approximation of the 
second phenomenon (as I understand this stuff):
https://www.mdpi.com/2076-3417/11/3/1348

BTW, more work in the kitchen besides boiling water you will find with 
google and a possible German translation of 5-sided vortex (5-eckiger 
Strudel ;)

Best regards
Michael


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From: Bald Eagle
Subject: Re: Petaled / polygonal vortex
Date: 28 May 2024 17:35:00
Message: <web.66564d09ea664b221f9dae3025979125@news.povray.org>
MichaelJF <fri### [at] t-onlinede> wrote:

> > I found some papers may be related to this question.

Bravo!

I read the entirety of the Feynman paper that Ingo linked, but other than being
an enjoyable and education read, it didn't really seem like it hinted at the
polygonal vortex.

The papers you found are describing just what I was seeing!
I'm somewhat amazed that it's "a thing"!  :D

I might have to see if the same effect happens with RT water, or if the boiling
needs to be happening to observe the effect.
I hadn't even really thought about doing more in terms of viscosity or speed of
stirring.

The math paper will probably take me a good long time to digest and start work
on.

"Bill, where have you been for the past week?"

"I was boiling water...."


- BW

This also reminds me of the science papers that I found that explored pigmented
water drops evaporating on a flat surface, and the spontaneous knotting of a
string when shaken in a box.

Science.


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