[alpharays]

I want to study exhaust gas streamlines behavior exit from exhaust pipe/tip. So, I put a vehicle in a tunnel which similar to aerodynamics (drag coefficient study).
My question for simulation in idle condition (car not running) what is the best setting for
1) tunnel inlet
2) tunnel outlet - pressure outlet??
3) tunnel wall - wall/slip??
4) tunnel floor (ground) - wall/no-slip??

Thanks
alpharays