Do we need separate two-phase solver?

[robertsawko]

I am growing more and more confident that we do need a separate two phase solver which works with PBEDiameter. Currently we are combining twoPhaseEulerFoam with PBE library to deliver new models, but this has several drawbacks which I will keep listing here:

• redundant solution of phase continuity equation,
• inconsistent properties, especially surface tension (surface tension is used in interfacial calculations, but in breakup/coalescence models).

[robertsawko]

Perhaps this is not necessary. The redundancy can be removed by not solving one fewer equation in PBE.