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# [femm] Problems with axisymmetric problems

- To: femm <femm@egroups.com>
- Subject: [femm] Problems with axisymmetric problems
- From: Werner Scholz <e9426502@student.tuwien.ac.at>
- Date: Mon, 04 Oct 1999 14:23:03 +0200
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    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@student.tuwien.ac.at
    URL: http://atp6000.tuwien.ac.at/MAGNET/WS/

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