[berkmm]

Hello everyone,
i'm working on a 2D fluent project. In this project I have a varying temperature gradient profile which changes towards x-axis. I wrote an UDF for this profile but I still dont know some variables. Do you have any UDF learn source about DEFINE macros and variable definitions? Can you please check my UDF? Temperature profile and UDF given in the below.

0 - 100 meter => 283.15+1.4*x
100-1000 meter => 420.93+0.0222*x
1000-1100 meter => -1006.9 + 1.45*x
1100-2000 meter => 557.59 + 0.0278*x
2000-2090 meter => -3164.6 + 1.8889*x
2090-2140 meter => -5068.9 + 2.8*x

#include "udf.h"


DEFINE_INIT(temp_init, domain)
{
cell_t c;
Thread *ct;
real pos[ND_ND];

/* loop over all cell threads in the domain */
thread_loop_c(t,d)
{
begin_c_loop_all(c,ct)
{
C_CENTROID(pos,c,ct);
if ( pos > 0 && pos < 100)
C_T(c,ct) =283.15 + 1.4*pos
else if ( pos >= 100 && pos < 1000)
C_T(c,ct)= 420.91 +0.0222*x
else if (pos >= 1000 && pos < 1100)
C_T = -1006.9 + 1.45*x
else if (pos >= 1100 && pos < 2000)
C_T = 557.59 +0.0278*x
else if ( pos >= 2000 && pos < 2090)
C_T = -3164.6 + 1.8889*x
else
C_T = -5068.9+ 2.9*x
}
end_c_loop_all(c,ct)
}
}

[AlexanderZ]

logic is correct, you have problems with C coding

first use pos or x in your code.
don;t forget ; and the end of each command

I recommend always compile the code, so you will see all problems in log output

[berkmm]

Thanks for everyone. For those who want to know the solution of this process here is my UDF code

#include "udf.h"
DEFINE_INIT(my_init_func,d)
{
cell_t c;
face_t f;
Thread *t;
real xc[ND_ND];

/* loop over all cell threads in the domain */
thread_loop_c(t,d)
{
/* loop over all cells */
begin_c_loop_all(c,t)
{
C_CENTROID(xc,c,t);
if (xc[0] > 0 && xc[0] < 100)
C_T(c,t) = 283.15 + 1.4*xc[0];
else if (xc[0] > 100 && xc[0] < 1000)
C_T(c,t) = 420.91 +0.0222*xc[0];
else if (xc[0] > 1000 && xc[0] < 1100)
C_T(c,t) = -1006.9 + 1.45*xc[0];
else if (xc[0] > 1100 && xc[0] < 2000)
C_T(c,t) = 557.59 +0.0278*xc[0];
else if (xc[0] > 2000 && xc[0] < 2090)
C_T(c,t) = -3164.6 + 1.8889*xc[0];
else 
C_T(c,t) = -5924.9+ 3.2*xc[0];

}
end_c_loop_all(c,t)
}
}

I now want to learn that what might be the difference between face loop and cell loop? which one will be more precise in terms of temperature definition? In patch initialization method, what looping method does it use? Do you have any ideas?

[AlexanderZ]

face loop and cell loop are totally different things
face loop is a loop over faces of boundary
cell loop is a loop over cells inside zones

you may use these macros depends on your needs
For more details look into Ansys Fluent Customization manual

if we speak about patch tool, I believe it use cell loop