outlet boundary condition CONFUSE!
 

Hi

Basically I'm simulating a very simple case of two-phase liquid-liquid flow in pipe using Fluent. Because in reality the pipe itself is very long so my geometry in the simulation is only a small part of the pipe. In this case [B]what boundary condition should I use for outlet?

Fluids are water and silicone oil,
multiphase VOF model
Laminar regime

Boundary condition of inlet is velocity-inlet, one fluid is entering the whole cross-section of inlet into the pipe which is pre-filled with another fluid.

Thanks a lot.