phase molecular weight derivative calculations

[ver2king]

My concern is within the following file, and the code snippets below:

https://github.com/GEOSX/GEOSX/blob/cadc47703f3936f8cff304a10c7ece9168b4c3cc/src/coreComponents/constitutive/fluid/CO2BrineFluid.hpp

// 4.1 Compute the phase molecular weights (ultimately, get that from the PVT function)

real64 phaseMolecularWeight[numPhase]{};
real64 dPhaseMolecularWeight[numPhase][numComp+2]{};

real64 phaseMolarDens{};
stackArray1d< real64, numComp+2 > dPhaseMolarDens( numComp+2 );

m_phase1.density.compute( pressure,
                          temperatureInCelsius,
                          phaseCompFraction.value[ip1].toSliceConst(), phaseCompFraction.derivs[ip1].toSliceConst(),
                          phaseMolarDens, dPhaseMolarDens.toSlice(),
                          false );
phaseMolecularWeight[ip1] = phaseDensity.value[ip1] / phaseMolarDens;
for( integer idof = 0; idof < numComp+2; ++idof )
{
  dPhaseMolecularWeight[ip1][idof] = phaseDensity.derivs[ip1][idof] / phaseMolarDens - phaseMolecularWeight[ip1] * dPhaseMolarDens[idof] / phaseMolarDens;
}

m_phase2.density.compute( pressure,
                          temperatureInCelsius,
                          phaseCompFraction.value[ip2].toSliceConst(), phaseCompFraction.derivs[ip2].toSliceConst(),
                          phaseMolarDens, dPhaseMolarDens.toSlice(),
                          false );
phaseMolecularWeight[ip2] = phaseDensity.value[ip2] / phaseMolarDens;
for( integer idof = 0; idof < numComp+2; ++idof )
{
  dPhaseMolecularWeight[ip2][idof] = phaseDensity.derivs[ip2][idof] / phaseMolarDens - phaseMolecularWeight[ip2] * dPhaseMolarDens[idof] / phaseMolarDens;
}

I could not interpret the formula behind these derivative calculations nor locate anywhere in the GEOSX documetation that mentions this aspect. May anyone help me understand the formulations behind those calculations?

[francoishamon]

What about discussing all your questions at once, on Zoom? That will be more efficient
Would that work for you?

[ver2king]

@francoishamon that shall work for me, and I do appreciate your swift response. Please just inform me of your availability and I shall share the Zoom meeting link.

[francoishamon]

Monday, Tuesday, or Wednesday afternoon next week?

[ver2king]

Just as a side note, I am located in the US CST time zone. Do you mean US CST or another time zone?

[francoishamon]

I meant US Pacific Time if that works for you

[ver2king]

Then, nevermind, not a huge difference to be fair. I am available on Monday & Wednesday afternoons next week. Therefore, I shall send the Zoom link for Monday afternoon sometime tomorrow (i.e., Friday 03/03/2023).