[femm] Problems with axisymmetric problems

[Werner Scholz <e9426502@xxxxxxxxxxxxxxxxxxxx>]

At the Vienna University of Technology we are making experiments with
magnetic pulse fields. Essentially, the pulse has the shape of a damped
cosine and we wanted to compare the experimental results with time
harmonic solutions of Maxwell's equations as a first approximation. I
have used FEMM to calculate the eddy currents in copper and iron
samples. For cylindrical samples the results are comparable, but for
spherical samples we have found rather large differences.

After some searching in the library I found an analytical solution for
the eddy current density in a sphere in a homogeneous sinusoidally
varying magnetic field. The results for "large" spheres (around 5 cm)
are in excellent agreement. However, small spheres of a few millimeters
in diameter, which have been used in our experiments, give unreliable
results.

You can have a look at my report at
http://atp6000.tuwien.ac.at/MAGNET/WS/projects/projects.html#proj3

There are links to HTML, PDF, and PostScript versions of my report,
a Mathematica notebook for evaluating the analytical solution, and
a zip file with my FE models for femme.

I welcome any comments!

In addition, the new release 2.1a of femmview seems to display wrong
eddy current densities. For example, the eddy current density does
not vanish at r=0. However, if the results of fkern 2.1a are displayed
with femmview 2.1, everything seems to be alright. But I have not tested
the new version more thoroughly, yet.

Here are some more links to the most interesting parts of my report:

Analytical solution for spheres and comparison with numerical FE
solution:
http://atp6000.tuwien.ac.at/MAGNET/WS/projects/proj3/node10.html

The analytical solution can be found in reference 7:
http://atp6000.tuwien.ac.at/MAGNET/WS/projects/proj3/node13.html

My FE models for femme are shortly described here:
http://atp6000.tuwien.ac.at/MAGNET/WS/projects/proj3/node14.html

The Mathematica notebook exported to HTML can be found here:
http://atp6000.tuwien.ac.at/MAGNET/WS/projects/proj3/node15.html

My comments on release 2.1a are on this page:
http://atp6000.tuwien.ac.at/MAGNET/WS/projects/proj3/node11.html

Kind regards

-- 
Werner Scholz
email: e9426502@xxxxxxxxxxxxxxxxxxxx
URL: http://atp6000.tuwien.ac.at/MAGNET/WS/