average temperature of a face

smukh · December 6, 2018, 18:12

Hello all,

I am trying to find the average temperature of a face of a cube which is going to be used as inlet temperature to another domain.
I am modelling a cube of stagnant water with inlet boundary condition at 323K. The output of my udf to calculate average temperature is coming zero!

DEFINE_ADJUST(avg_temp,d) /*calc outlet temp average of water*/
{
real tavg=0.0;
face_t f;
real A[ND_ND];
real area = 0.0;
real area_tot = 0.0;

Thread *t = Lookup_Thread(d,7);

begin_f_loop(f,t)
{
F_AREA(A,f,t);
area = NV_MAG(A);
area_tot+=area;
tavg+=F_T(f,t)*AREA;
}
end_f_loop(f,t)
tavg/=area_tot;
printf("avergae temperature of outlet of water is %f\n", tavg);
printf("area total = %f\n", area_tot);

}

I am new to udf and would appreciate any help with this udf. Thank you!

obscureed · December 6, 2018, 20:21

Hi Smukh,

Assuming you've pasted your code accurately, the first error to look at is
tavg+=F_T(f,t)*AREA;
because "AREA" is not the same as "area". (C language is case-sensitive.) This should not get past a compiler without some warnings, or maybe errors. Please can you debug this and tell us what happens next? Does your code report a sensible value of area_tot?

This UDF is suitable only for serial Fluent, of course.

I would discourage use of "printf" in UDFs -- "Message" is safer. The difference is possibly small, but not necessarily.

Good luck!
Ed

smukh · December 10, 2018, 16:57

Hi Ed,

Thank you for your suggestions. I have successfully resolved it. It worked when I changed from DEFINE_ADJUST to DEFINE_EXCUTE_AT_END and AREA to area. I am not sure why I wasn't getting the value even after changing caps area, it was giving me no error while compiling. But as I did not need values for every iteration I was fine by replacing adjust by at end.

December 6, 2018, 18:12	average temperature of a face	#1
smukh New Member on Join Date: Nov 2018 Posts: 3 Rep Power: 8	Hello all, I am trying to find the average temperature of a face of a cube which is going to be used as inlet temperature to another domain. I am modelling a cube of stagnant water with inlet boundary condition at 323K. The output of my udf to calculate average temperature is coming zero! DEFINE_ADJUST(avg_temp,d) /calc outlet temp average of water/ { real tavg=0.0; face_t f; real A[ND_ND]; real area = 0.0; real area_tot = 0.0; Thread t = Lookup_Thread(d,7); begin_f_loop(f,t) { F_AREA(A,f,t); area = NV_MAG(A); area_tot+=area; tavg+=F_T(f,t)AREA; } end_f_loop(f,t) tavg/=area_tot; printf("avergae temperature of outlet of water is %f\n", tavg); printf("area total = %f\n", area_tot); } I am new to udf and would appreciate any help with this udf. Thank you!

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December 6, 2018, 20:21		#2
obscureed Senior Member Join Date: Sep 2017 Posts: 246 Rep Power: 12	Hi Smukh, Assuming you've pasted your code accurately, the first error to look at is tavg+=F_T(f,t)*AREA; because "AREA" is not the same as "area". (C language is case-sensitive.) This should not get past a compiler without some warnings, or maybe errors. Please can you debug this and tell us what happens next? Does your code report a sensible value of area_tot? This UDF is suitable only for serial Fluent, of course. I would discourage use of "printf" in UDFs -- "Message" is safer. The difference is possibly small, but not necessarily. Good luck! Ed

December 10, 2018, 16:57		#3
smukh New Member on Join Date: Nov 2018 Posts: 3 Rep Power: 8	Hi Ed, Thank you for your suggestions. I have successfully resolved it. It worked when I changed from DEFINE_ADJUST to DEFINE_EXCUTE_AT_END and AREA to area. I am not sure why I wasn't getting the value even after changing caps area, it was giving me no error while compiling. But as I did not need values for every iteration I was fine by replacing adjust by at end.