the macro of c_face_loop and F_UDMI(F_UDSI)
 

When the following udf is operating, there is error such as:
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: ()
DEFINE_SOURCE(velocity_u_source,c,t,dS,i)
{
face_t f;
Thread *tf;
int n;
real S=0;
c_face_loop(c,t,n)
{
f=C_FACE(c,t,n);
tf=C_FACE_THREAD(c,t,n);
if (THREAD_ID(tf)==10)
{
F_UDSI(f,tf,0)=0.0;
}
}
return S;
}
And check it. When F_UDSI(f,tf,0) is repalced by C_UDSI(c,t,0), the operation is ok. Does this mean that F_UDSI(F_UDMI) cound not retrieved as faces of cell is looped with the macro of c_face_loop?
If I want to access some faces of cell, which method can be used??
Thanks.

F_UDSI can on be used as an RHS of the =



you can't read values into it unfortunately

And check it. When F_UDSI(f,tf,0) is repalced by C_UDSI(c,t,0), the operation is ok. Does this mean that F_UDSI(F_UDMI) cound not retrieved as faces of cell is looped with the macro of c_face_loop?
If I want to access some faces of cell, which method can be used??


you should not you F_UDSI as well as C_UDSI to monitore your variables.
UDSI means user defined scalar not monitor.
On the other hand, you may use F_UDMI/C_UDMI for that task, user defined memories. F_UDMI should handle your problem

more information regarding UDMI and UDSI you may find in Ansys Fluent Customization manual

best regards