In CFX manual, it says that for the flow with bouyancy effect if the reference pressure is not zero, then the hydrostatic portion is not included in the output pressure by CFX-POST. By numeric value check, however, I found that

enthalpy change = Cp*(T2-T1) = Cv*(T2-T1) + [(Pref+Ps+rho*g*h)/rho]1 - [(Pref+Ps+rho*g*h)/rho]2

where Ps is the pressure from CFX-POST.

while Cp*(T2-T1) is not equal to Cv*(T2-T1) + [(Pref+Ps)/rho]1 - [(Pref+Ps)/rho]2

I was wondering why hydrostatic pressure is not included in the output pressure, but it is included in the output enthalpy from CFX-POST. Can anyone explain this to me?

Expert parameter:

Name pressure reference value Type Real Default Value 0 Description The relative pressure to set at the pressure reference node.

I think now I know the reason. The enthalpy is calculated from the absolute pressure, and the hydrostatic portion is included in the absolute pressure. I have checked the numeric values in CFX-POST for this already.

Thank you for your suggestion, but I am sorry I can't understand. Could you explain me in more details?