I noticed when I was boiling pasta the other day that the pasta uniformly spread out and formed a donut like torus. Why does this happen? Does it have to do with the shape of the pot? I tried to take a picture when it was boiling, but steam got all over my lens. So, this is a more 2d version of what the pasta looked like with boiling (while boiling, the pasta strands were uniform and seemed to be repelled out uniformly from the center of the pot.
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2$\begingroup$ What type of pasta? Spaghetti? $\endgroup$– jinaweeJun 19, 2014 at 23:31
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2$\begingroup$ Could you take a picture of this phenomenon? $\endgroup$– hpekristiansenJun 20, 2014 at 0:01
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$\begingroup$ How do you stir it? $\endgroup$– Kyle KanosJun 20, 2014 at 0:03
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$\begingroup$ I edited it I am sorry about the ersatz. Perhaps if you have time you can try for yourself.But I did not stir it this time, just as @Kyle Kanos commented on; The Torus was not as uniform as it usually was, but it was still rather obviously a torus with the hole in the center, as if a current was flowing out from the center equally in every direction. $\endgroup$– GödelJun 20, 2014 at 1:07
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$\begingroup$ What kind of stove do you have? Because an electrical heat due to conduction of heat, while a gas stove due convection, which also would heat the walls of the pot more. $\endgroup$– fibonaticJun 24, 2014 at 21:28
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1 Answer
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The walls of your pot act like a thermal sink that transfers heat to the surrounding environment. Therefore, the water temperature gets hotter as you move towards the center of the pot. The cold water then sinks and the hot water pushes up through the center, creating the donut-like torus you are describing.
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$\begingroup$ Plus I bet the heat is only applied in the very center of the bottom of the pot. A copper pot base or a large, electrically heated stovetop might disrupt the effect. $\endgroup$– user10851Jun 20, 2014 at 3:10
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$\begingroup$ But wouldn't this pull the spaghetti inwards at the bottom? My theory would be that there would be more boiling (gas state) water rising from the center which pushes the spaghetti to the sides. $\endgroup$ Jun 24, 2014 at 21:26
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$\begingroup$ @Chris White: What equipment would I need to record a vector field of my stove top's electrical ouput? I am really interested by this idea. And how would that transfer to the pot (the stove is comprised of electrical coils). $\endgroup$– GödelJun 27, 2014 at 0:16