Udf - Periodic Boundaries
 

I have searched the forums for a few weeks now but cannot find any relevant information on this so I finally signed up to ask.

I am creating a UDF to form a periodic boundary condition for inlet/outlet boundaries of different lengths. The basic UDF file I have written is below;-

#include "udf.h"

DEFINE_PROFILE(x_velocity_inlet, thread, index)
{
real x[ND_ND];
face_t f;
real Uvel[ND_ND];
real Vvel[ND_ND];
Domain *domain;
Thread *tf;

int Zone_ID=3;
domain=Get_Domain(1);
tf= Lookup_Thread(domain, Zone_ID);

begin_f_loop(f, tf)
{
Uvel[1]=F_U(f, tf);
Vvel[1]=F_V(f, tf);
}
end_f_loop(f, tf)

begin_f_loop(f, thread)
{
F_PROFILE(f, thread, index) = (Uvel[1]);
}
end_f_loop(f,thread)
}


This seems to work for just the x-velocity components. I have tried linking the Y-velocity as;-

F_PROFILE(f, thread, index) = (Uvel[1], Vvel[1]);

However the results are the same.

Eventually this will be done in 3D for a multiphase flow. If there are any useful posts/websites/guides out there then please feel free to just point me in the right direction. I would be happy to answer any questions and GREATLY appreciative of any help you could give me.

Thanks,
Ern

It should be noted that the outlet boundary has a zone id of 3.

The UDF interprets however it is clear that there is no velocities passed to the inlet as there is no mass flow in or out of the VOF. As though the inlet and outlet are just walls.

Could someone confirm if I am referencing the F_U (X-velocity) and F_V(y-velocity) correctly?

Hi!

I think in this case need a two UDF both U and V velocity components.

Alex.