[aozdogan]

Hi all,
I am trying to write a udf code to define boundary conditions for the inlet and outlet temperature that are varying with time. I create a txt/or c file, but I dont know how to read this file. Does anyone have experienced with this type problem?

Thanks

[Kokemoor]

You might be able to use profiles instead of UDFs. They're less powerful, but simpler. Check out Section 6.6 of the Fluent User's Guide.

[macfly]

I would go for a DEFINE_PROFILE udf, see the examples in sections 2.3.19.10 and 2.3.19.11 of the UDF Manual release 15.0. Then read section 2.3.19.12 in order to know how to hook the boundary profile in your model.

[aozdogan]

Originally Posted by macfly

I would go for a DEFINE_PROFILE udf, see the examples in sections 2.3.19.10 and 2.3.19.11 of the UDF Manual release 15.0. Then read section 2.3.19.12 in order to know how to hook the boundary profile in your model.

thanks Kokemoor and macfly.
I went over all you mentioned here, but none of them has an example related to my problem. Since my experimental data is a large demand even though I cut off using monthly base temperature vs time, the best way to assign this data to fluent is to have txt file and read it by udf. I am still stuck how to manage

[macfly]

Example 2.3.19.11 is perfectly related to your case with time-varying specification of a profile. If your case has a lot of time steps and a lot of if(CURRENT_TIME <= ...) you could automate the writing of the UDF in Python, Matlab or any other programming language.

[aozdogan]

thanks macfly! your are right it is exactly matching with my problem except that I have a lots of case file.I looked at the fluent 14.5 release but I just found fluent 15. Anyway, finally I got my code is working know. Here is my code;
#include "udf.h"
#include "mem.h"
double time;
double timef[51], temp1f[51], temp2f[51];
int vcount=0;
FILE *fp;
DEFINE_INIT(read_file, d)
{
/*reads data from file and stores as global variables*/
int i;
fp=fopen("timevstemp.txt", "r");
for (i=0;i<51; i++){
fscanf(fp,"%lf %lf %lf", &timef[i], &temp1f[i], &temp2f[i]);
}
fclose(fp);
printf(" %f %f %f %\n", timef[0], temp1f[0], temp2f[0]);
}
DEFINE_PROFILE(tempout, t, nv)
{
face_t f;
double x[ND_ND];
int row1=1; /*initalize row to 1*/
int prow1=0;
double Tout;
time=CURRENT_TIME;
while((time) >= timef[row1] ){
row1=row1+1;
}
prow1=row1-1;
Tout= 273.15+ temp1f[prow1] + ((time)-(timef[prow1]))*(temp1f[row1] - temp1f[prow1])/
(timef[row1]-timef[prow1]);
printf(" Tout %f temp1 %f tempf %f \n",Tout, temp1f[prow1], temp1f[row1]);
begin_f_loop(f, t)
{
F_CENTROID(x,f,t);
F_PROFILE(f,t,nv)= Tout;

}
end_f_loop(f,t)
}
DEFINE_PROFILE(tempin, t, nv)
{
face_t f;
double x[ND_ND];
int row1=1; /*initalize row to 1*/
int prow1=0;
double Tin;
time=CURRENT_TIME;
while((time) >= timef[row1] ){
row1=row1+1;
}
prow1=row1-1;
Tin= 273.15+ temp2f[prow1] + ((time)-(timef[prow1]))*(temp2f[row1] - temp2f[prow1])/
(timef[row1] - timef[prow1]);
begin_f_loop(f, t)
{
F_CENTROID(x,f,t);
F_PROFILE(f,t,nv)= Tin;

}
end_f_loop(f,t)
}