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Energy density definitions

Posted 14 déc. 2021, 03:17 UTC−5 Acoustics & Vibrations 4 Replies

Max Käfer
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Hi together, in Comsol there are some energy densities, which can be generated for an output. The normal energy density, kinetic energy density and the elastic energy density. Can anyone help me out how they are mathematically defined here in Comsol? Thank you very much, Max

4 Replies Last Post 15 déc. 2021, 13:20 UTC−5
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 3 years ago 14 déc. 2021, 05:10 UTC−5

Hi, the best is that you turn on "Equation View" (in the display options or in your Preferences) and look into the formulas, most of the energy variables are fields depending on (t,x,y,z) ("t" might not be applicable in your case, it depends on the solver being used) hence must be integrated over your domains. Some are total values (it's in the name and the description) hence are already integrated, mostly over the full defined model.

You will also find more info in the doc under the respective physics chapters.

Have fun COMSOLing Sincerely, Ivar

-------------------
Have fun COMSOLing,
Sincerely,
Ivar
Hi, the best is that you turn on "Equation View" (in the display options or in your Preferences) and look into the formulas, most of the energy variables are fields depending on (t,x,y,z) ("t" might not be applicable in your case, it depends on the solver being used) hence must be integrated over your domains. Some are total values (it's in the name and the description) hence are already integrated, mostly over the full defined model. You will also find more info in the doc under the respective physics chapters. Have fun COMSOLing Sincerely, Ivar
Max Käfer
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Posted: 3 years ago 15 déc. 2021, 02:15 UTC−5
Updated: 3 years ago 15 déc. 2021, 02:16 UTC−5

Hi Ivar, thank you very much for ur reply. I still couldn't find the physical formulas for the energie densities in the results so far. In the appendix there is a screenshot where I'm searching for those values. Maybe I missed something or I was searching in the wrong place. Yours sincerely, Max

Hi Ivar, thank you very much for ur reply. I still couldn't find the physical formulas for the energie densities in the results so far. In the appendix there is a screenshot where I'm searching for those values. Maybe I missed something or I was searching in the wrong place. Yours sincerely, Max
Max Käfer
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Posted: 3 years ago 15 déc. 2021, 02:16 UTC−5
Updated: 3 years ago 15 déc. 2021, 02:56 UTC−5

Hi Ivar, thank you very much for ur reply. I still couldn't find the physical formulas for the energie densities in the results so far. In the appendix there is a screenshot where I'm searching for those values. Maybe I missed something or I was searching in the wrong place. Yours sincerely, Max

Hi Ivar, thank you very much for ur reply. I still couldn't find the physical formulas for the energie densities in the results so far. In the appendix there is a screenshot where I'm searching for those values. Maybe I missed something or I was searching in the wrong place. Yours sincerely, Max
Dave Greve
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Posted: 3 years ago 15 déc. 2021, 13:20 UTC−5

Try printing out a report, I usually use intermediate. You will find full expressions for everything.

Try printing out a report, I usually use intermediate. You will find full expressions for everything.

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