Outlet boundary conditions (Simflow GUI)
 

Hello
I'm a beginner in using OpenFOAM, and I'm trying to simulate a heated wall cylinder through which air is flowing. I'm quite unsure on which boundary condition I should use in the outlet, as the "Pressure inlet-outlet velocity" requires me to assume there's no pressure drop and the "inlet-out" I can't understand very well what it is.
Any advice?