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# Re: [femm] Solenoid Model

- To: femm@yahoogroups.com
- Subject: Re: [femm] Solenoid Model
- From: David Meeker <dmeeker@foster-miller.com>
- Date: Fri, 11 May 2001 10:33:34 -0400
- Organization: Foster-Miller, Inc.
- References: <D135CB6636D3D411B88C0008C75DFDD971C2DF@val4.hrtextron.textron.com>

    "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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    org:Foster-Miller, Inc.;Electrical and Electronic Systems Group
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    email;internet:dmeeker@foster-miller.com
    title:Senior Engineer
    adr;quoted-printable:;;350 Second Avenue=0D=0A;Waltham;MA;02451-1196;USA
    fn:David Meeker, Ph.D.
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- References:
  - RE: [femm] Solenoid Model
    - From: "Achmad, Mike" <machmad@hrtextron.textron.com>

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