[bietchetlien1995]

Hello every one! I'm a newbie in the using the Fluent.
Now I'm do my research about CFD - simulating the wind flow over the building and check the result with real wind tunnel test.
(I'm looking for anyone who now is doing, we can more discuss).

About my question.
How can I put the wind velocity in the Fluent if it changes depending on the height!

Thank you so much!

[LuckyTran]

Using PROFILES


or UDF

[sufjanst]

You can create a Inlet Profile using matlab or python (or whatever language you want). The profile includes the x,y,z coordinates and the value. You can import it to fluent and set is as a BoCo.

Or you can use a UDF like LuckyTran said.

[bietchetlien1995]

pls give me anywhere I can study about this one? thank you!

[sufjanst]

Just write a profile of an existing simulation in fluent and you can see the syntax of a profile. Try do adapt it to your profile and that's it.

[Roh]

To export a profile and see how Fluent write a profile:


File>Export>Profile...


To import your profile after writing one of them and use it in your simulation:


Boundary conditions> Profiles...


After importing your profile, you can see the profile in the drop-down list of your parameter e.g. velocity and select it. For example I've showen in the below screenshot, the temperature profile that use in my project.









But if your profile varied depend on any other parameter, you need to write a UDF to change the profile. It's so simeple. Read this page:




https://www.sharcnet.ca/Software/Flu...udf/node42.htm




Hope this helps!

[bietchetlien1995]

Thank Roh!
I thought it's better if I define a UFD, the main thing here, I'm not so familiar with C language!

[bpulat]

I believe if you read what LuckyTran linked in the previous answers you can pretty much do it yourself.

Using PROFILES


or UDF

You don't need to fully understand C to work with fluent UDF.
I will give another link to you where you can try to adapt this to your case.
Example
If there is still a problem with your UDF, post here again with your code so we can help it.

[bietchetlien1995]

#include "udf.h"
DEFINE_PROFILE(log_velocity,thread,index)
{
real y[ND_ND];
real x,z;
face_t f;
begin_f_loop(f,thread)
{
F_CENTROID(y,f,thread);
x = y[1];
z = y[2];
if (x<2)
{
F_PROFILE(f,thread,index) = 0.;
} else {
F_PROFILE(f,thread,index) = 26.22*log(x/2)/log(149.5/2);
}
end_f_loop(f,thread)
}
}



Here I found out in the internet and all ready modified and it worked.
By the way, I wanna ask about, what is the F_centroid mean? And if we create the geometry it will wrong if we move the central of axises. (x,y,z) Right?

[bietchetlien1995]

Btw, thank all of you so much!

[bpulat]

This link will help out with your first question : Face Macros
For the second question i didn't understand what you really meant about being wrong.

[LuckyTran]

I am appalled that you went straight to the non-intuitive UDF instead of the intuitive PROFILE, which was only a few button clicks and you would have been done days ago. You're such a masochist! And you must love spending a lot of time doing things!

Btw I hope you know that y[0],y[1], and y[2] are the (1st,2nd,3rd) coordinates which are normally (x,y,z). Of course you are free to use whatever variable names you like.

F_CENTROID is a macro returning the coordinates at the centroids of the faces in the thread specified. These coordinates belong to the global system, so if you move the geometry around, they will follow it.

[bietchetlien1995]

Oh man! LuckyTran!
I'm not that type, when I came here to ask, I already watched some video about UFD. So, my brain just wanted to finish them perfectly. And the code just in C language, so it made me hard, if ANSYS uses the mathlab, maybe be I've done long time ago. ^^
Btw, your answer was so great! are you a Vietnamese?