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UDF: CONTROL DRAG/EXCHANGE COEFF

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Old   June 4, 2004, 00:47
Default UDF: CONTROL DRAG/EXCHANGE COEFF
  #1
Luis
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Hi everyone,

I am solving a 2-phase flow, and need to control the drag using an UDF.

I am trying to apply the DEFINE_EXCHANGE_PROPERTY macro to define the drag coefficient. When I use my UDFs for a simple case, without important direction changes, the results are reasonable. However, for a more complex geometry, even if the UDF is written with the same equations that are presented in the Fluent documentation, I get weird flow patterns, which I don't see if I use a pre-defined Fluent drag model.

Has anyone been successful controlling the drag / exchange coefficient using an UDF?

Any help will be extremely appreciated,

Luis
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Old   June 6, 2004, 14:37
Default Re: UDF: CONTROL DRAG/EXCHANGE COEFF
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ap
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This sounds strange. I'd check the code, because the DEFINE_EXCHANGE_PROPERTY just replaces the predefined FLUENT drag function.

Try to follow the example reported in UDF manual.

To control the value, just define a UDM and store the value returned by the UDF there. You can then plot using contours for example.

Hi

ap
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Old   June 8, 2004, 12:05
Default Re: UDF: CONTROL DRAG/EXCHANGE COEFF
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Luis
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Hi ap,

Thanks for your answer.

Before writing the UDF I read carefully the examples, and I esentially tried to follow one of them.

My UDF returns the exchange coefficient, instead of the drag function, but I think that's what you meant.

Checking the UDF returned values sounds like a good idea, I'll try that.

Regards, Luis
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Old   June 8, 2004, 13:29
Default Re: UDF: CONTROL DRAG/EXCHANGE COEFF
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ap
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Yes, I meant the drag coefficient. Sorry for the misunderstanding.

Hi

ap
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Old   July 16, 2012, 06:27
Default Udm
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Majid Mostafazadeh
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Hi
How did you make a UDM for DEFINE_EXCHANGE_PROPERTY?
UDM needs to be made in a loop, how did you write that loop?
Thank you
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