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-   -   UDF: CONTROL DRAG/EXCHANGE COEFF (http://www.cfd-online.com/Forums/fluent-udf/33881-udf-control-drag-exchange-coeff.html)

Luis June 4, 2004 00:47

UDF: CONTROL DRAG/EXCHANGE COEFF
 
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

ap June 6, 2004 14:37

Re: UDF: CONTROL DRAG/EXCHANGE COEFF
 
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

Luis June 8, 2004 12:05

Re: UDF: CONTROL DRAG/EXCHANGE COEFF
 
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

ap June 8, 2004 13:29

Re: UDF: CONTROL DRAG/EXCHANGE COEFF
 
Yes, I meant the drag coefficient. Sorry for the misunderstanding.

Hi :)

ap

forgottenman July 16, 2012 06:27

Udm
 
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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