How to model sudden expansion
 

Hi all,

I am busy modelling air flow through a huge pipe. Actually the pipe is just the last part of a pretty simple model.

Dia = 1m
Length = 100m
Velocity at inlet = 10m/s

The outlet of the pipe is at atmosheric pressure. Is there a special boundary in OpenFOAM that can take into account the sudden expansion at the outlet (like a head loss or vent or..) or do I actually have to model a bit of atmoshpere to take this into account? See the attached image.

Many thanks,

Karl