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5 Replies
Last post: August 27, 2010 6:36am UTC
August 25, 2010 1:08pm UTC
Lorentz force
Hi,
with the new v4.0a, I miss the predefined Lorentz forces in the AC/DC module. In magnetic field mode (mf), there is at least the Lorentz force mf.FLtz_xyz. In magnetic and electric field mode (mef), there is no Lorentz force predefined.
I also miss time-averaged Lorentz force that was available in earlier versions.
Nevertheless, I found the time-averaged Lorentz force in "cold crucible" from the model gallery...maybe because this is translated from 3.5a??
Or did I miss anything, a hidden checkbox maybe?
Thanks
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August 25, 2010 2:18pm UTC in response to mb
Re: Lorentz force
Hi
I couldnt find them either, but there are still some "missings to come" mentionned in the ACDC relase notes, so it could be that 3D Lorentz forces and mef/ec expressions will be completed in the next relase
--
Good luck
Ivar
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August 25, 2010 2:30pm UTC in response to Ivar Kjelberg
Re: Lorentz force
Again, thanks for your kind support!!
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August 26, 2010 2:53pm UTC in response to Ivar Kjelberg
Re: Lorentz force
Hi!
Indeed, we are working on bringing back these and other expressions, as well as introducing new ones. Feel free to send your suggestions directly to support@comsol.com, to help us prioritize our efforts.
Best regards,
Linus
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August 27, 2010 6:15am UTC in response to Linus Andersson, COMSOL Employee
Re: Lorentz force
Hi again,
again looking at it, it seems that the (time/phase-dependent) Lorentz force has wrong units. It should be a volume force density N/m^3 more than a force in N as it comes from F_L=J x B. Copying the implemented definition to a new variable definition gives N/m^3.
Best, Marcel from rainy Berlin
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August 27, 2010 6:36am UTC in response to mb
Re: Lorentz force
Hi
Yes I have also seen this one and reported it to support, they were aware about it as indeed there are still a few units errors in there, you can see it in the equations if you turn them on (as units are redefined and not calculated for internal variables). They told me that they will fix this for next release.
Actually if you calculate it out fully yourself by a volume integration using the J and B, then the units will be right, but via the internal Lorentz force FL you will have a [m] error in the units
--
Good luck
Ivar
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