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March 5, 2010 3:31pm UTC

Modelling AC currents in 2D axi

Hello;

i would like to model a circuit (hollow cylinder for example) with current flowing in the r-z plan and not in the azimutal direction (phi) which is the default setting in Comsol multiphysics. (The magnetic field would be along phi and not in the plane).
I thought that i could write the PDE equation and adapt the ampere law with no current in the phi direction.
But, the PDE formulation is not available in 2D axi. why? (is it because it is only available in the AC/DC module?)

Best regards

benjamin

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March 5, 2010 4:13pm UTC in response to Benjamin Lepers

Re: Modelling AC currents in 2D axi

Hi,

thanks a lot, but do you know if with the AC/DC module in 2D axi you can choose the current direction (phi or r-z plan?)

Best regards

benjamin

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March 8, 2010 8:17am UTC in response to Ivar K

Re: Modelling AC currents in 2D axi

Hi

the current could be defined as a function of r. The structure that i try to model is an axi symetric hollow conical horn. There is a current flowing in the inner and outer conductor. This produces a toroidal magnetic field. (B is in, out the plan only function of r and z). In DC mode, we can defined an inward current in the r-z plan.


Regards

benjamin

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March 8, 2010 9:45am UTC in response to Benjamin Lepers

Re: Modelling AC currents in 2D axi

Hi,

i have seen in the AC/DC book that we can choose between the 2D in plane currents application modes and meridional currents mode with the currents present in the rz plane. That's exaclty what i need!


regards

benjamin

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March 8, 2010 1:18pm UTC in response to Benjamin Lepers

Re: Modelling AC currents in 2D axi

Hi

In my undrstanding, the meridional or toroidal current selection are usefull for solving the magnetic field, but in your cse it's simply Joules heating, no? then its less critical this should work correctly for 2D axi.

I would also go for the "segregated solver" as you problem can be split, and for the moment you have not linked the temperature to the material properties.

But with these powers you will end up vaporising your system (in steady state) if you do not cool it better.

Finally take care when workg in 2D axis,: you have to get the units to match, you need to often multiply by "2*pi*r" the "loop length" for units coherence.
This should be done explicitely in your formulas for the integration variables, but can be selected with a "click" for the postprocessing.

Always carefully check the units to be sure you havnt forgotten the 2*pi*r !!

And do your homework with simple analytical formulas to be sure you have the correct orders of magnitude for your results

Good luck
Ivar

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