Boundary condition
 

I'm a new user of Fluent & working with catalytic converter system. I have a problem in defining a boundary condition of inner tube (inlet A & outlet B) in catalytic converter. Can I define A & B as another inlet and outlet? or any possible solution? My catalytic converter illustrated as follow (please ignore the '0'). The actual inlet and outflow is actually much smaller however its dificult to draw here.

000000_________________________________________

---000000000_________________________

inlet 0000 A 000000000000000000000000 B 0000 Outflow

---000000000_________________________

000000_________________________________________

Thanks