The long blades at the last stage of modern steam turbines are prone to flutter. Typically steam condensation has occurred by the last stage. However, ideal gas is usually assumed when performing flutter analysis for steam turbines. The accuracy of the flutter analysis can be improved by considering the flow effects of the steam condensation.
RPMTurbo has developed an equilibrium wet steam flow model that accounts for steam condensation. Flow properties such as pressure, temperature, speed of sound and viscosity of wet steam are calculated using formulae from The International Association for the Properties of Water and Steam. The plot below compares the steam quality (steam mass fraction) calculated by RPMTurbo at the exit of an industrial steam turbine with data from the manufacturer (published with permission).