[skel_1]

The following is a UDF that I am using to calculate the spreading radius and height of a droplet impingement on a surface. It is an axisymmetric problem and I am trying to evaluate the above values at every time-step.



#include <udf.h>
DEFINE_EXECUTE_AT_END(execute_at_end)
{
real r[ND_ND];
real time=CURRENT_TIME;
real temp, y,x;
face_t f;
cell_t c1;
Thread *t, *t1;
FILE *fp;
c1=F_C1(f,t);
t1=THREAD_T1(t);
begin_c_loop(c1,t1)
{
temp=C_VOF(c1,t1);
if(temp==0.5)
{
C_CENTROID(r,c1,t1);
x=r[0];
y=r[1];
fp=fopen("spread ratio.txt","w");
fprintf(fp,"%5.10d %5.8d %5.8d",time,x,y);
fclose(fp);
}
}
end_c_loop(c1,t1)
}


Fluent compiles the UDF properly. I hook up the UDF it up at the Execute at end and initialize the solution. Then I am patching the liquid droplet with a velocity. Once I start iterating this is the error that Fluent pops up:

Updating solution at time level N...
Global Courant Number : 0.01
done.
physical-dt 1.0000e-008
iter continuity x-velocity y-velocity time/iter
1 0.0000e+00 1.6108e-03 1.5012e-04 0:00:00 1
1 0.0000e+00 0.0000e+00 0.0000e+00

Error:
FLUENT received fatal signal (ACCESS_VIOLATION)
1. Note exact events leading to error.
2. Save case/data under new name.
3. Exit program and restart to continue.
4. Report error to your distributor.
Error Object: ()

PLEASE HELP!!

This same problem was working properly without the UDF