[guitarbren]

Hi Everyone, first post so be gentle

I've been trying to model a chimney in OpenFOAM and have successfully generated a mesh using snappyHexMesh and background mesh. Now in blockmeshdict I have defined the 'floor' as a fixedwall, frontandback to be empty (2D case) and the sides (including roof) to just 'patch'.

I'm wondering what conditions to apply to these boundaries so it mimics a real life chimney sitting in a desert somewhere! I.e. enabling flow to come and go as necessary through the 'ceiling' and 'sides'.
I've tried giving initial conditions such as temperature and pressure a zeroGradient type in the 0 directory but it still models the entire scenario as if it is in a fixed box - is there an easy way to do this?

Any help would be greatly appreciated!
Bren