Timeline for Estimating the Characteristic Time of Spinning Tea
Current License: CC BY-SA 4.0
12 events
| when toggle format | what | by | license | comment | |
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| May 24, 2023 at 3:01 | vote | accept | Ashmit Dutta | ||
| Apr 22, 2023 at 18:10 | answer | added | Martin Gales | timeline score: 1 | |
| Nov 6, 2022 at 6:00 | history | tweeted | twitter.com/StackPhysics/status/1589135493530271746 | ||
| Nov 6, 2022 at 3:32 | history | edited | Qmechanic♦ |
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| Nov 6, 2022 at 2:30 | comment | added | FlatterMann | Flow has to be laminar, right? Other than that I can't see what else could be wrong. Maybe the assumption that flow stays laminar in a large vessel is wrong because of Reynolds number. I have no intuition for where that transition might occur (in terms of angular velocity). So, yeah, intuition is largely unreliable. | |
| Nov 6, 2022 at 2:25 | comment | added | Ashmit Dutta | Yes that is a fair point. Though one thing to note is that I took the assumption of $H\gg R$ so there would be a large amount of water with a lot of initial kinetic energy. Perhaps there is some other force/phenomenon taking play in larger fluids though. | |
| Nov 6, 2022 at 2:17 | comment | added | FlatterMann | I have a bit of a doubt about the result because if we take the same geometry with ten times the radius, then the spin down time constant suddenly becomes over an hour. That does not gel with my intuition about how water in a large drum behaves. The dimensional analysis is correct, though. I guess I need to get myself a really large tub of water... | |
| Nov 6, 2022 at 1:51 | comment | added | FlatterMann | I will leave the checking to a theoretician, but I might do the experiment with tea, later. I wonder if English Breakfast behaves differently from Earl Grey? | |
| Nov 6, 2022 at 1:44 | history | edited | Ashmit Dutta | CC BY-SA 4.0 |
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| Nov 6, 2022 at 1:43 | comment | added | Ashmit Dutta | Oh you are completely right. For the experiment as well as the calculations, I used room temperature water as a substitute. Though even if the tea was hot, I think since the time scale was so short, we could say the temperature and viscosity remains constant. Also I have added a derivation with my calculations if you want to check if there is a factor of 2 missing. | |
| Nov 6, 2022 at 1:32 | comment | added | FlatterMann | Viscosity is a function of temperature. Was the tea hot? Did the spin down time constant decrease as it cooled down? Other than that the ratio between observation and theory is suspiciously close to a factor of two... | |
| Nov 5, 2022 at 23:52 | history | asked | Ashmit Dutta | CC BY-SA 4.0 |