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Old   August 26, 2006, 17:08
Default Compiled UDFs - questions
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I'm a rookie on the UDF subject and I have some questions.

1) I want to impose a Neuman boundary condition (velocity gradients), possibly through the DEFINE_ADJUST macro. Do I have to interpret it or compile it??

2) When using compiled UDFs, do I need to compile the source file BEFORE loading it in Fluent?

3) Can I compile using the devc++ compiler or is it not compatible with Fluent?

I'm using Fluent 6.2.16 and Windows XP.

I would appreciate any help!! Antonis
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Old   August 26, 2006, 20:19
Default Re: Compiled UDFs - questions
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Will try to answer some of your questions.

1) you wont be able to implement a boudnary condition using a DEFINE_ADJUST macro. You will only be able to change boundary conditions using DEFINE_PROFILE. It will be very difficult to implement a Neumann boudary condition in Fluent.

2) you can interpret the source code which doesnt require a compiler although it runs slower than compiling. I would recommend compiling.

3) I'm not sure about this one. Its easiest just to compile within fluent.
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Old   August 27, 2006, 07:52
Default Re: Compiled UDFs - questions
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Thanks for your answer.

For the Neumann condition, you mean it will be difficult to implement it through a interpreted UDF, or in general?

Also another question:

When setting a boundary conditions, should I loop over the cells of the boundary, or the face?

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Old   August 27, 2006, 12:50
Default Re: Compiled UDFs - questions
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For the Neumann condition, I think it will be difficult to implement at a wall because fluent does not allow you to access the boundary condition using UDF as far as i know. I have done something similar using two-phase flow and ended up using UDS equations to do it.

For setting boundary condition, you loop over all the faces on the boundary of interest. fluent stores values on the faces at the domain boundary and cell centroid in the interior
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Old   August 28, 2006, 11:03
Default Re: Compiled UDFs - questions
Albert F.
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I tryed to compile UDF using dev c++ but it didn't worked. As far as I know you need to install .Net framework and make a few changes at enviroment settings. If you want look for a post called error while compiling udf, I posted the instructions I followed to solve compilers problems.
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Old   August 29, 2006, 08:36
Default Re: Compiled UDFs - questions
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@cadaei: I don't want to implement the Neumann condition at a wall, but at a velocity inlet (in fact I want to impose the 2d zero vorticity condition du/dy=dv/dx).

@Albert F.: thanks, I found the previous thread, very helpful.
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Old   December 26, 2012, 07:12
Satish Gupta
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Rahul123 is on a distinguished road
Can anyone tell me how to apply du/dy=0 at a boundary using UDF.
I cannot understand how to differentiate between du/dx and du/dy
thank you
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