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# RE: [femm] simple femm, feed back appreciated.

- To: <k.gregory@lboro.ac.uk>
- Subject: RE: [femm] simple femm, feed back appreciated.
- From: "John D. Ayer" <john_d_ayer@yahoo.com>
- Date: Mon, 3 Feb 2003 16:16:18 -0500
- Cc: "Femm@Yahoogroups. Com" <femm@yahoogroups.com>
- Importance: Normal
- In-reply-to: <5.2.0.9.0.20030203192656.00b121b8@staff-mailin.lboro.ac.uk>
- Reply-to: <john_d_ayer@yahoo.com>

    Hi Keith:

    This is exactly the kind of feedback I wanted, Thank you.

    You applied a periodic boundary condition and enlarged the area boundary for
    the air space.

    I can understand enlarging the area boundary. I can understand changing the
    boundary to a circle. After careful reading of Apendix C.3 in the manual I
    believe I understand applying the periodic boundary condition to the area
    boundaries.

    Making the mesh the same size in both areas is just common sense since the
    problem is so easy the number of nodes in the air space will not bog down
    the computer.

    Sometimes it takes a very simple example to get the point across.

    Do you have a good reference source for understanding the boundary
    conditions for magnetic analysis and they way they are referenced in FEMM?

    Thanks

    John D. Ayer

    -----Original Message-----
    From: Keith Gregory [mailto:k.gregory@lboro.ac.uk]
    Sent: Monday, February 03, 2003 2:36 PM
    To: femm@yahoogroups.com
    Subject: Re: [femm] simple femm, feed back appreciated.

    John,

    A few points:

    You have no boundary conditions set. The boundary is a bit close to the
    problem if it was intended to be open. The mesh density set inside the
    magnets was a bit fine and the density outside the magnets a bit course for
    what you are trying to do.

    I have modified your file using the Kelvin Transformation type of open
    boundary and made the mesh densities the same inside and outside the
    magnets. If you compare this to your original I think you will see the
    difference.

    Keith.

    At 07:50 03/02/2003 -0500, you wrote:
    >Hi:
    >
    >This is a very simple femm model of 2 magnets with opposing forces. I
    would
    >like to know if I set this model up correctly to understand the interaction
    >between 2 magnets with opposing forces.
    >
    >The goal is just to better understand how to use the FEMM tool. From doing
    >the tutorials, reading the manual and "lurking" on the news group I believe
    >the model to be properly set up.
    >
    >Being a manufacturing engineer and designer my experience with analysis is
    >limited to simple static FEA for stress and this model is designed to test
    >my understanding of basic magnetic analysis. I can swap different
    materials
    >in and out, change boundary conditions and do simple experiments and see
    how
    >the results of the FEMM relate to my simple experiments.
    >
    >John D. Ayer
    >
    >
    >
    >
    >Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
    >

    Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/

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    - From: Keith Gregory <k.gregory@lboro.ac.uk>

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