Stagnation pressure in 2-phase flow

[Frankenshtein]

I'm trying to figure out stagnation pressure and mass flow quality for a horizontal 2-phase water/steam pipe. I can get x˙0\dot{x}_0x˙0 once i know p0p_0p0, but i can't find a good way to calculate p0p_0p0 itself.
Any tips or references?

 

[nineothree6]

I had the same problem during my grad project on geothermal flow. To find p0 in two-phase flow, I started with the homogeneous equilibrium model (HEM). It assumes both water and steam move at the same speed and pressure. You might also look at Hewitt and Hall-Taylor's work on annular flow, they have helpful formulas. If you're using software, REFPROP or CoolProp can give good starting values.