Boundary condition
 

I want to simulate a rectangular tunnel flow which has inlet and outlet velocities with k-omega model. The tunnel is long enough so the flow can be considered as full-developed.My question is how to set the inlet and outlet boundary condition to get good simulation.

Actually I know how to set k and omega of the inlet through the empirical equation. But I am not very sure of the outlet boundary condition setting in some books. So can anybody give me a more accurate description of the outlet setting?
Any reply will be appreciated.


Regards

xiaojun