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adjusting gravity using UDFs

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Old   May 5, 2002, 21:08
Default adjusting gravity using UDFs
  #1
chriss
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I need to adjust gravity every time step. Using Scheme this is straight forward but I can find how to do it using UDFs.

Any ideas.

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Old   May 6, 2002, 02:31
Default Re: adjusting gravity using UDFs
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Henrik Widell
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The M_gravity[ND_ND] array in models.h holds the gravity vector, so you can change gravity by changing the values in this array. I need no "include models.h" statement, I think, since this header file seems to be included through udf.h - but I might be mistaken on this.

ND_ND is 2 for a 2D case and 3 for a 3D case...

Regards,

Henrik
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Old   May 6, 2002, 23:07
Default Re: adjusting gravity using UDFs
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chriss
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Great.

Will that work with interpreted UDF's? I tried referencing M_gravity[0] with and without #include "models.h" and the preprocessor complained.

Thanks.
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Old   May 7, 2002, 02:01
Default Re: adjusting gravity using UDFs
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Henrik Widell
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What version are you using? In FLUENT 6 M_gravity is in models.h, but in FLUENT 5 it is in flow.h - both should be included if you have included udf.h though.

Will it work in interpreted UDFs? To be honest, I don't know - I gave up using the interpreted UDFs long ago, because of all the limitations and bugs. A C compiler isn't that expensive...and it saves me a lot of grief.

Henrik
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Old   May 8, 2002, 08:09
Default Re: adjusting gravity using UDFs
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Greg Perkins
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If that doesn't work, you can always add the gravity as a source term = pg to the momentum equations using your own udf. I haven't done this but I can't see why it wouldn't work.

Of course, modifying the internal gravity vector is a bit better if its possible for your interpreted udfs.

I too think compiled udfs are the way to go - interpreted stuff is generally more of a hassle. Also, I've found a unix/linux platform better than a Windows platform.

Greg
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