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A comment on Cooling a cup of coffee with help of a spoon. Parent comment

Re:Cooling a cup of coffee with help of a spoon by gjm11 on Thursday February 17, 2011 @07:09AM (#2230640)
Your aim is to make sure that every bit of the coffee eventually makes it to the surface (so that the highest-energy molecules there can escape and cause cooling). If you stir regularly then (roughly) each bit of the coffee just moves in a circle, and parts that start out below the surface stay below the surface. If you stir it at random, then (this is probably a theorem, if you define "random" with a bit of care, and it probably doesn't require all that much randomness) any portion of the coffee ends up eventually at any given place.

So I think your intuition is doing pretty well.

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Re:Cooling a cup of coffee with help of a spoon by khafra on Thursday February 17, 2011 @08:17AM (#2230779)
Surely there are some regular motions which could be approximated using a spoon which would more efficiently move the hottest parts of a liquid to the surface than random turbulence? My intuition says sliding the spoon down the side of the mug, then turning the flat side upward and lifting it in the middle of the mug would be one such more efficient motion.

Does anybody have a supercomputing cluster we could use to run an optimizing search across a whole bunch of fluid flow simulations?

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Re:Cooling a cup of coffee with help of a spoon by pbhjpbhj on Thursday February 17, 2011 @12:24PM (#2231785)
>My intuition says sliding the spoon down the side of the mug, then turning the flat side upward and lifting it in the middle of the mug would be one such more efficient motion.

You're still going to be getting laminar flow unless you're lifting fast enough to eject the tea from the cup (which I assume is contrary to the rules). I use a forward and backward motion going from low down at one side to high up at the other (especially when stirring hot soup for my little nearly 2yo) - I'm trying to produce a ragged (turbulent) collapsing void of air, maximising the surface area exposed particularly in producing as much turbulence as possible at the surface. One tends to get spiralling voids at either edge of the spoon.

I wonder if you can stir fast enough to produce cavitation and what effect that would have on the results.

Also can I design my own spoon to use?

-

http://en.wikipedia.org/wiki/Cavitation

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Re:Cooling a cup of coffee with help of a spoon by apl on Thursday February 17, 2011 @08:53AM (#2230870)
I got one, but unfortunately it's still working on the milk-or-tea-first conundrum.
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Re:Cooling a cup of coffee with help of a spoon by JonnieCache on Thursday February 17, 2011 @09:13AM (#2230945)
>milk-or-tea-first

Ahhhhh, the one debate more divisive than emacs-or-vim.

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Re:Cooling a cup of coffee with help of a spoon by zwieback on Thursday February 17, 2011 @12:02PM (#2231678)
Right, what I remember from Thermo II 20 yrs ago is that heat transfer in turbulent flow is higher than in laminar flow. Heat transfer is basically deltaT * someFactor, with someFactor depending on a ton of parameters. One of them is whether it's laminar or turbulent.
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