[Ahmed A. Serageldin]

I write a UDF to read data of two variables (building load and flowrate), I saved data for each variable in a separate text file. Then by using Define_IN_Demand macros to open and read each one. Then these data are used to calculate inlet conditions by using DEFINE_PROFILE macro as shown here, then I compiled the UDF successfully and hooked the profile then start the simulation and after 1 iteration I got this error " Reversed flow on 1407 faces (56.3% area) of pressure-outlet 37.
Stabilizing temperature to enhance linear solver robustness.
Stabilizing temperature using GMRES to enhance linear solver robustness.

Divergence detected in AMG solver: temperature
Divergence detected in AMG solver: temperature
Divergence detected in AMG solver: temperature
Divergence detected in AMG solver: temperature
Divergence detected in AMG solver: temperature
Divergence detected in AMG solver: temperature
Divergence detected in AMG solver: temperature
Divergence detected in AMG solver: temperature
Divergence detected in AMG solver: temperature
Divergence detected in AMG solver: temperature
Divergence detected in AMG solver: temperature
Divergence detected in AMG solver: temperature
Divergence detected in AMG solver: temperature
Divergence detected in AMG solver: temperature
Divergence detected in AMG solver: temperature
Divergence detected in AMG solver: temperature
Error at host: floating point exception

===============Message from the Cortex Process================================

Compute processes interrupted. Processing can be resumed.

================================================== ============================

Error: floating point exception
Error Object: #f"

But when I read only building data from text file and considering flow rate as constant there is no error and the simulation completed without any error.
Please help me to solve this problem

UDF used

#include "udf.h"

#define cp 4182

real Q[87600];
real m[87600];
real avetempa=279.65;

DEFINE_ON_DEMAND(read_buildingdata)
{
int i;
float b;
FILE *rfile; /* declare a FILE pointer */
#if RP_HOST
host_to_node_sync_file("test1.dat");
#endif
#if RP_NODE
host_to_node_sync_file("/");
#endif
rfile = fopen("buildingdata.txt", "r"); /* open file for reading */
#if RP_HOST
Message("buildingdata file opened\n");
#endif
for (i=0;i<87600;i++)
{
fscanf(rfile, "%f\n", &b); /* that supposes one value per line */
Q[i]=b;
}
fclose(rfile);
#if RP_HOST
Message("buildingdata file closed\n");
#endif
}
DEFINE_ON_DEMAND(read_flowdata)
{
int ii;
float d;
FILE *rfile1; /* declare a FILE pointer */
#if RP_HOST
host_to_node_sync_file("test2.dat");
#endif
#if RP_NODE
host_to_node_sync_file("/");
#endif
rfile1 = fopen("flowratedata.txt", "r"); /* open file for reading */
#if RP_HOST
Message("flowrate file opened\n");
#endif
for (ii=0;ii<87600;ii++)
{
fscanf(rfile1, "%f\n", &d); /* that supposes one value per line */
m[ii]=d;
}
fclose(rfile1);
#if RP_HOST
Message("flowrate file closed\n");
#endif
}

/* Defining outlet temperature.*/
DEFINE_ADJUST(average_exit_temp,domain)
{
real tempa=0.0;
real totalarea=0.0;
int ID1 = 43;//'108; /* the outlet boundary condition identifier*/
int ktt=N_TIME-1;

#if !RP_HOST
face_t f1;
real A[ND_ND];
Thread *outlet_thread = Lookup_Thread(domain,ID1);

begin_f_loop(f1,outlet_thread)
{
if PRINCIPAL_FACE_P(f1,outlet_thread)
{
F_AREA(A,f1,outlet_thread);
totalarea +=NV_MAG(A);
tempa +=NV_MAG(A)*F_T(f1,outlet_thread);
}
}
end_f_loop(f1,outlet_thread)

#if RP_NODE
tempa = PRF_GRSUM1(tempa);
totalarea = PRF_GRSUM1(totalarea);
#endif

avetempa= tempa/totalarea;
if(ktt==0) avetempa=283.45;
# endif

node_to_host_real_1(avetempa);

#if RP_HOST
/*Message("average temperature : %f K q7=%f\n",avetempa,Q[ktt]);*/
#endif
}

DEFINE_PROFILE(Inlettemp,thread,pos)
{
face_t f;
real x[ND_ND],btt;
real ftime = CURRENT_TIME;
int k_time=N_TIME;
real qheat=Q[k_time-1];
real COP;
real qhp;
real m;
real w;

if(qheat<0)
COP=3.6857+0.1*(avetempa-273.15);

else
COP=9.4867-0.158*(avetempa-273.15);

if(qheat<0)
qhp=(qheat-(qheat/COP))/(m*cp*60);

else
qhp=(qheat+(qheat/COP))/(m*cp*60);


#if RP_NODE
begin_f_loop(f, thread)
{
if PRINCIPAL_FACE_P(f,thread)
{
if(ftime<3600) btt=283.45;
else btt = avetempa +(qhp);
F_PROFILE(f, thread, pos) =btt;
}
}
end_f_loop(f, thread)
#endif
}

[pakk]

You read mass flow from the file, but you never use it anywhere... Or at least after reading the code three times, I can not see where it is used.

You do use an uninitialized m in your define_profile.

So I guess the m should refer to the value from the file, or not?

[Ahmed A. Serageldin]

Originally Posted by pakk

You read mass flow from the file, but you never use it anywhere... Or at least after reading the code three times, I can not see where it is used.

You do use an uninitialized m in your define_profile.

So I guess the m should refer to the value from the file, or not?

I used m to calculate qhp at the end of UDF

[pakk]

Originally Posted by Ahmed A. Serageldin

I used m to calculate qhp at the end of UDF

No, you don't.
Maybe you want to, but there you redefine m ("real m") and never tell Fluent what m is.

You have to find out which face you are in, which index of your array m that corresponds to, and then refer to that value.

[Ahmed A. Serageldin]

Originally Posted by pakk

No, you don't.
Maybe you want to, but there you redefine m ("real m") and never tell Fluent what m is.

You have to find out which face you are in, which index of your array m that corresponds to, and then refer to that value.

Thank you so much, your advice is very useful and solve my problem