Pressure Outlet B.C.
 

Hi I'm using commercial codes (CFX and Fluent). In both cases there is the possibility of setting "Pressure outlet" B.C. It is not clear to me what are in this case the B.C. set to the other variables (i.e. Temperature) at domain exit. Is there a general rule for the B.C. to be set at Pressure Outlets for the other variables (Temperature, velocities, species) or is it "code-dependent" ?

Thanks

Max

Re: Pressure Outlet B.C.
 

(1)."code-dependent?", you should be able to get your own conclusion easily, by solving the same problem using both codes and the same outlet conditions. (2). I have no idea what's in the code.

Re: Pressure Outlet B.C.
 

Generally when the static pressure is set at the outlet the implication is a nozzle or duct type of flow. In this case the other variables are extrapolated from the upstream field points. The entrance conditions need to be set consistent with this outlet BC. Typically one sets the entrance total pressure, total temperature and direction cosines for the velocity components. I do a slight variation on the exit pressure BC. I set the exit pressure as a linear combination of the desired exit pressure and the static pressure at the nearest field cell. This allows the internal field to relax to the specified pressure without forcing it to be exactly set. This allows the flow to carry some curvature out through the exit. This approach usually allows for rapid convergence