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Re: [Question #698392]: I calculated the kinetic energy by E=0.5mv^2+0.5Iw^2 but it is not equal to kineticEnergy() when O.cell.velGrad is set

To: yade-users@xxxxxxxxxxxxxxxxxxx
From: Jan Stránský <question698392@xxxxxxxxxxxxxxxxxxxxx>
Date: Tue, 17 Aug 2021 09:25:44 -0000
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Question #698392 on Yade changed:
https://answers.launchpad.net/yade/+question/698392

    Status: Open => Answered

Jan Stránský proposed the following answer:
Hello,

both values are computed differently.
E=0.5*m*v^2+0.5*I*w^2
of course still holds, but the values of "v" and "w" are different.
Have a look at source code [2]: conditions "if (scene->isPeriodic)", variables like "spin = scene->cell->getSpin()" and their usage, comments "Only take in account the fluctuation velocity" etc.
If still anything is not clear, please let us know.

If you think this discrepancy should be mentioned in the documentation,
feel free to update it yourself or create and issue on gitlab pages of
the project (not to be forgotten).

Cheers
Jan

[2] https://gitlab.com/yade-
dev/trunk/-/blob/master/pkg/dem/Shop_01.cpp#L193

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