[gzamiri@gmail.com]

hi everybody
I want to simulate far field boundary for incompressible flow. in my model , far field boundary is circle. in each step time, I want fluent to specify inlet and outlet boundary. for this purpose, I consider this condition:
if:
1. u.n<0 inlet boundary
2.u.n>0 outlet boundary

n is normal vector, u is velocity vector.

I would like to know how could I apply this condition in fluent. I guess I should develop a UDF do you think that my way is correct?

I appreciate your help!

my udf is as follows:


/* UDF for determination of inlet and outlet */
#include "udf.h"
#include "sg.h"

DEFINE_EXECUTE_AT_END(determination_boun)
{
Domain *d;
face_t f;
Thread *t;
real velocity_vector[2], mag_velocity, normal_vec, mag_normal_vec;
real A[ND_ND], ds, es[ND_ND], A_by_es, dr0[ND_ND];
real X_component,Y_component, Guage_Pressure;
d=Get_Domain(1);
int ID=12; /*Zone ID for farfield zone from boundary condition task page*/
t=Lookup_Thread(d,ID);
begin_f_loop(f,t)
{
/* find velocities*/
velocity_vector[0]=F_U(f,t);
velocity_vector[1]=F_V(f,t);

/* magnitude of velocity vector*/
mag_velocity=NV_MAG(velocity_vector);
/* magnitude of normal vector*/
/*BOUNDARY_FACE_GEOMETRY(f,t,A,ds,es,A_by_es,dr0);*/
F_AREA(A,f,t);
mag_normal_vec=NV_MAG(A);
/* attack angle*/
double teta=0;
if((mag_velocity* mag_normal_vec*cos(teta))<0)
{
X_component=F_U(f,t); Y_component=F_V(f,t);
}
else
{
Guage_Pressure=F_P(f,t);
}
}
end_f_loop(f,t)
}