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ntfluxInt - kinks in plot

Posted 22 avr. 2020, 19:57 UTC−4 Heat Transfer & Phase Change, Results & Visualization Version 5.3a 2 Replies

Laura G Aerospace Engineering
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I want to simulate a block of aluminum that has a certain temperature and radiates to an empty space. So I set up a COMSOL simulation:

  • Physics: heat transfer in solids, time dependent

  • I created a simple block

  • added a material (Aluminum 6063-T83)

  • set the temperatures (delta is 10K)

  • turned on surface-to-surface radiation

  • all surfaces of the block are diffuse surface with a given epsilon of 0.5

  • mesh is physics controlled (coarser)

When I do so I get reasonable results (I verified them by hand), but I noticed some kinks in the temperature plot. I investigated that they result from even bigger kinks in the ntfluxInt global value (see graph). I already varied the mesh sizes, time steps, material, and several other parameters, but none of that removes the kinks.

So my question is: where do these kinks come from? Are they simulation errors? Is there any way to get rid of them?

Thanks for your help

2 Replies Last Post 23 avr. 2020, 14:41 UTC−4
Friedrich Maier COMSOL Employee

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Posted: 5 years ago 23 avr. 2020, 02:19 UTC−4
Updated: 5 years ago 23 avr. 2020, 03:59 UTC−4

Dear Laura,

such phenomena can occur if the time stepping is not appropriate set. Please control the time stepping in the time dependent solver as described here: https://www.comsol.com/support/knowledgebase/1254

Kind regards
Friedrich

Dear Laura, such phenomena can occur if the time stepping is not appropriate set. Please control the time stepping in the time dependent solver as described here: https://www.comsol.com/support/knowledgebase/1254 Kind regards Friedrich
Laura G Aerospace Engineering
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Posted: 5 years ago 23 avr. 2020, 14:41 UTC−4

Setting the relative tolerance to a smaller value worked perfectly. Thanks for your help!

Setting the relative tolerance to a smaller value worked perfectly. Thanks for your help!

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