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• #8451
Azmir
Participant

The total pressure in a multicomponent system is given by

P = (rho1 + rho2)/3 + (g11*psi1^2 + g22psi2^2 + g12*psi1*psi2 + g12*psi2*psi1)/6

What would be the pressure for a single component?

In a single component LBM the pressure is,

P = rho/3 + g11*psi1^2/6

How do you interpret the additional two terms (g12*psi1*psi2) that appear in multicomponent LBM in the context of partial pressures?

#8456
TimBingert
Participant

Hi Azmir,

please be aware that thermodynamically speaking, in a multicomponent mixture, there are no “partial pressures”. The partial pressure is just a simplification of a component’s fugacity in the mixture which is related to the component’s chemical potential. I would recommend to derive a free energy (Helmholtz energy) from the bulk pressure term you showed above and then derive chemical potentials for components 1 and 2. As you are using the pseudopotential model, you need to take into account how the psi_i are a function of the rho_i.
All in all, this looks like another mixing rule for a multicomponent equation of state.

Kind regards
Tim

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