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Old   October 10, 2011, 10:29
Default UDF temperature profile
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Delmas Anthony
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Hello all,

My question will maybe seem quite easy for some of you, but i've never used UDF before and i'm a little lost, especialy cause i don't know either how to code in this language.
Anyway, to make short, i have the temperature values of a wall surface, obtained experimentatly. Now i would like to implement them in the simulation.

I have for ex:
x=0.1cm T=350K
x=0.2cm T=367K
x=0.3cm T=389K....

How can i put all these values in my simulation via UDF?

Thanks all for your future helps.
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Old   January 9, 2012, 06:11
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Hi Anthony,

I also have to specify the temperature profile (fixed in time) at a wall and do not know how...
how did you solve the problem? Might you copy the udf file you wrote to specify wall temperature?

Thank you very much!!

Serse
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Old   January 9, 2012, 06:41
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I would insert a Profile rather than an UDF. try it!
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Old   January 9, 2012, 09:10
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Delmas Anthony
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I solved the problem by finding the polynomial equation feeting with my points. I found this equation with Matlab.
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Old   January 13, 2012, 13:33
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I tried with the following profile file to simulate a linearly increasing temperature at a wall

((temperature line 2)
(x
-0.3955 0.682 )
(y
0.0795 0.0795 )
(temperature
1173.15 1923.15 )
)

The file simply contains locations of two nodes and temperature values at these nodes. Fluent reads it easily, but after initializing the solution there is not such temperature distribution at the wall. The temperature I get is the one from the fluid zone.

Might you help me on this?

For NeoGamaes - How did you include the polynomial function at a wall?

Thank you very much!
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Old   January 16, 2012, 04:10
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Exemple of Temperature profile:

Code:
/*************************************************************************/
/* temperature_profile2_100.c                                                          */
/* UDF for specifying a temperature profile boundary condition for the disk */
/*************************************************************************/

#include "udf.h"


DEFINE_PROFILE(temperature100disk, thread, index) 
{
  real x[ND_ND];		/* this will hold the position vector */
  real y;
  face_t f;

  begin_f_loop(f, thread)
    {
      F_CENTROID(x,f,thread);
      y = x[1];
        F_PROFILE(f, thread, index) = (-3363080951743./1000000000)*y*y+(426743./10000)*y+(3710751./10000);
    }
  end_f_loop(f, thread)
}
If your wall is horizontal in Fluent, you just have to replace x by y. To find the polynomial function with Matlab, use the "polyfit" and "polyval" function.. it's really easy.
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