HYD Fluid Properties calculation

HYD Fluid Properties calculation We consider four different cases to compute the HYD Fluid Properties:

Case 1:	P > Psat	there is no vapor and all air/gas is dissolved
Case 2:	PHvap < P < Psat	there is no vapor and part of the air/gas is dissolved and part free
Case 3:	PLvap < P < PHvap	there is some vapor and ALL the air/gas is free
Case 4:	P < PLvap	there is vapor and air/gas but NO LIQUID

The main assumptions are:

• The “air/gas content” and “saturation pressure” do not vary with time or position.

• The volume of the free air/gas/vapor is assumed to vary with pressure in a way determined by a constant polytropic index Γ.

Liquid with dissolved gas volume assumption We assume that the unit volume of liquid still occupies a unit volume when the air/gas is dissolved in it:

In other words, the small molecules of air/gas “hide” between the bigger molecules of liquid. The air/gas molecules do not increment the volume but they do increment the mass.