TOUGH3 vs TOUGH2-MP Printout of Mass fractions in single phase
Our understanding is that adding all component mass fractions of a phase add up to one. In TOUGH3 (or at least using eos3), it would appear that this is not the case. For example, we observe that when an element is fully (liquid) saturated, the mass fractions of components in gas phase are all zero (and therefore do not add up to one). In TOUGH2-MP, we would still get hypothetical mass fractions of components in gas phase, and they would add up to one even in elements which are fully (liquid) saturated. Is our interpretation of the mass fraction printouts in both TOUGH2-MP and TOUGH3 correct? Has there indeed been a change? In essence, we are moving form TOUGH2-MP to TOUGH3, and are validating some of our own test cases, which includes comparing the component mass fractions. If my understanding is correct, is there an easy means of porting the same definition of mass fraction to TOUGH3?
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When a phase saturation is 0.0, the mass fractions inside the phase is meaningless. In such case, they may be simply assigned a 0.0 value or even not be taken care. In some EOS modules, mass fractions are calculated based the system temperature and pressure, not matter whether the phase exists.