Re: [femm] Solenoid Model

[David Meeker <dmeeker@xxxxxxxxxxxxxxxxx>]

"Achmad, Mike" wrote:

> Thanks for a useful example. I have run the solenoid model with the FEMM
> and could only get a force of -6.335N vs. -5.69N according to the virtual
> work method. Is this an acceptable difference or is this as the result of
> the improper selection of the contour in the femmview? There was also a
> small difference in the inductance calculation (7.78E-2 vs 7.25E-2 with
> Ansys?).
>
> Thanks again in advance for any comments.

I tried a couple of runs with finer mesh densities. The results were:
5027 nodes: F = -6.99 N, L = 80.125 mH
19675 nodes: F = -7.022 N, L = 80.360 mH

For comparison, I also ported the problem to the Quickfield 3.4a student
version. The results were:
495 nodes: F = -6.446 N, L = 77.142 mH
which is pretty much dead-on the results from femm with an equivalently coarse
mesh.

I don't know what is going on with respect to the numbers in the example. I
think that the example Ansys problem was just run on a really coarse mesh,
yielding low accuracy results. Someone actually put a discussion of this
example on the web at: http://www.rose-hulman.edu/~balichmd/lab3_ME522.html in
which the example solution was compared to a higher mesh density solution in
Ansys. That study concludes that the mesh is too coarse in the original Ansys
example to give a reliable answer.

Dave.


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