I am just trying to extract the y-velocity at x=0. Please note that when I use v=F_V(f,t) or F_U(f,t) instead of v=cte, I receive the following error. The line x=0 is within the domain, defined by using Surface menu.

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: ()

================================================== ========= #include "udf.h"

DEFINE_ADJUST(data_extract_from_jet,d) { real xx[ND_ND]; /* this will hold the position vector */ real x, y, u, v; Thread *t; face_t f; FILE *fp; fp = fopen("jet.dat","w");

thread_loop_f(t,d) /* loop over the Thread of Faces t in the domain */ { begin_f_loop(f,t) /*loop over the faces (f) of the Thread of Faces */ { F_CENTROID(xx,f,t); x = xx[0]; y = xx[1]; if( x==0)

{

v=F_V(f,t);

fprintf(fp, "\n x=%g y=%g\n vc=%g\n", x, y, v); } } end_f_loop(f,t) } fclose(fp); }

why dont use a DEFINE_ON_DEMAND function?

Thanks for your reply. Both Define_adjust and On Demand work. I guess the peroblem is from somewhere else.