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Old   January 27, 2010, 16:32
Default CFX Additional Variable Transport Equation
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I am interested in implementing a turbulence model into CFX.

I have done so in Fluent using UDFs and UDSs and found it somewhat easy.

In CFX, it appears that I need to use Additional variables and Junction Boxes.

CFX help has nothing like the UDF manual in Fluent. So I am trying to piece together.

One issue was the junction box implementation. It seems there used to be a tutorial with mesh deformation and FSI that had this. But I do not see the files for CFX.

Any guidance on examples for this would be appreciated

Thanks
Scott
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Old   January 28, 2010, 16:33
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Are you sure you can't do your model in CEL? The CEL in CFX is much more powerful than what is available in Fluent.
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Old   January 29, 2010, 14:05
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perhaps that would be best?

with fluent I am used to using a hook function that fills 30+ UDMs that are then used in the source calculations for my UDS

with CELs, I assume I would have to do a little more work in the setup portion (i.e. setup the expression for each "UDM")

if CELs are used for the additional variables are these updated in sequence after each iteration?
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Old   January 30, 2010, 05:36
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You have not described what you are modelling so I cannot say whether you can do it in CEL.

The Fluent UDM and UDS are additional variables in CFX. You have a few different options for how they are calculated - either an expression, a diffusion equation, a convection equation or diffusion/convection (there may be others but these are the ones I have used). At first glance a UDM is equivalent to an additional variable set by an expression, and a UDS is equivalent to an additional variable with a convection/diffusion equation.

From memory the CEL is updated before the coefficient loops. The CEL is not coupled into the equation solver, but any additional variables are (through a segregated solver).
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