Boundary problem
 

hi im trying to simulate a pipe system to attempt to model aircarft cabin ventilation.

What i want to do is have a inlet in the top left corner of the cabin, and an ouitlet in the bottom right. What im trying to do is have a pipe system after the outlet boundary which recirculates 50% of the fluid back into the cabin. However i cannot work out how you allow the flow to continue into the pipe after the putlet boundary. I have tried using 'exhaust fan' etc but im not sure if im doing it right. Im quite new to fluent so any help would be great. Thanks.