Force calculation gives N instead of N/m

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dnh37

dnh37

July 21, 2013 6:56am UTC

Force calculation gives N instead of N/m

Hi,

I draw two beams next to each other in cross-section (a 2D simulation) and apply 1V to one and 0V to the other, and solve for electric field. When I do a Force Calculation in COMSOL v4.3a for beam #1 I get 1.3e-11 N. When I do a force calculation for beam#2 I get the same number in negative form as I'd expect by symmetry. When I do a force calculation for a box containing both beams I get something near zero, as I'd expect. See attached file.

However my problem is, I was expecting to get a force-per-meter [N/m, not N]. Because integrating the stress tensor for such a 2D simulation should give force-per-meter, and then when you go to do a 3D simulation you apply that force-per-meter at each point along the z-dimension of the beam.

What is going wrong?

Thanks,
David

Attachments:   force between two beams.mph  

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Jens Krause

Jens Krause

July 22, 2013 6:52am UTC in response to dnh37

Re: Force calculation gives N instead of N/m

Hallo David,

the is a setting that specifies the thickness in the 3rd dimension and
force calculation are multiplied with this value. So instead of N/m
you get N.

Regards

Jens

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dnh37

dnh37

July 22, 2013 6:57am UTC in response to Jens Krause

Re: Force calculation gives N instead of N/m

Thanks. Where is this? I'm clicking around but can't see that anywhere.

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dnh37

dnh37

July 22, 2013 6:58am UTC in response to dnh37

Re: Force calculation gives N instead of N/m

Never mind, it's under Solid Mechanics node (or whatever type of simulation you choose).

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