CFD Online Discussion Forums - Time dependent wall temperature

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Time dependent wall temperature

Hi
I am interested to study heat transfer in a wall which one side of it has a known time dependent temperature. I know I have to create a UDF file to provide the temperature function I have, but I don't have programming experience. what C functions should I use in addition to Define_profile () ?

thanks

If the temperature is uniform then yes define profile could work. If you have non-uniform temperature then you have to use some sort of mapping.

Thanks, my temperatures are the experimental temperatures recorded during a whole day (24 hours), so it is non-uniform. Because I am new to FLUENT, I am just studying the UDF manual of FLUENT. Therefore I would appreciate if you kindly could explain some more. Thanks again for your help.

Hi,

See the Pressure Profile example in the DEFINE_PROFILE of the UDF guide:

Code:

/***********************************************************************

 UDF for specifying steady-state parabolic pressure profile boundary

 profile for a turbine vane

 ************************************************************************/

 #include "udf.h"

 DEFINE_PROFILE(pressure_profile,t,i)

 {

    real x[ND_ND];    /* this will hold the position vector */

    real y;

    face_t f;

    begin_f_loop(f,t)

      {

       F_CENTROID(x,f,t);

       y = x[1];

       F_PROFILE(f,t,i) = 1.1e5 - y*y/(.0745*.0745)*0.1e5;

      }

    end_f_loop(f,t)

 }

- x[ND_ND] stores the coordinates, so that the x coordinate is x[0], y is x[1] and z is x[2]
- the equation at the right of F_PROFILE(f,t,i) is what you have to establish from your data, some equation of temperature as a function of x,y,z (or x,y in 2D)
- then read about how to hook the DEFINE_PROFILE at the boundary, it is well explained in the UDF guide