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Ilker November 5, 2008 13:33


Is there is any file which gives parabolic velocity profile or function in Fluent database? If any, how can I change it into semi-parabolic profile which means it will have just (x,y) but not (x,y)? If there is no such a file in database how can I create it?

Thank You

Dothan November 5, 2008 13:48

I think you are talking about boundary condition UDF profile. Yes, Fluent can sets BC with all functions you prefer, time and spatial (2D and 3D) depend function. There are some examples on UDF user guide (ctrf+F makes miracles sometimes ),also in Fluentuser site, or send an e-mail to your Fluent seller. this is the step one. The second step is to be familiar with standard C. regards.

Ilker November 5, 2008 13:54

hmmm, Dothan I think you didnt understand my question. If you read well, you will see that I am searching a file which has been already given as parabolic velocity profile. Secondly, if there exist such file I would like to learn its name. And finally, I just wanted to learn a way to make it with semi-shaped, I didnt want to get C lessons.

Amod November 5, 2008 15:27


It is always wise to write UDF that suits your requirement. Copy-pase may not work. You may find a comprehensive article on UDF at


Ilker November 5, 2008 16:20

well, it shouldn't be hard to comprehend. I think there exists a parabolic velocity function in fluent folder. Something.h I want to find and change it. But I couldn't find this file, and my question is where is this damned file and what it is the name?

rajesh November 8, 2008 00:37

To my knowledge and working experience with fluent, there no predefined parabolic velocity profile in Fluent database. You need to write a UDF with the define macro DEFINE_PROFILE and specify the velocity. This is the best way to my knowledge.

Other way many do is .... create a straight pipe (separate simulation) with same diameter as that of the inlet (your simulation), and run a simulation to a parabolic velocity profile in the st. pipe. Use File->Write->profile, to write the velocity profile at the outlet of the st. pipe. Then read the velocity profile file in your simulation and use it for your inlet.

It is not clear from your statement ".... it will have just (x,y) but not (x,y)?"

ilker November 8, 2008 04:47

Thank you rajesh "not (-x,y),but (x,y)".I did mistake when I was writing.It means It won't have minus values of x, which means also that its shape will be the half of a normal parabola.

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