We should decide whether we want to refer to the expression:

$$\rho=(1-\phi)\rho_{\text{solid}}+\phi\sum_{c}\rho_c=(1-\phi)\rho_{\text{solid}}+\phi\sum_{c}\sum_{\ell=1}^{np}x_{c\ell}\rho_{\ell}s_{\ell}=(1-\phi)\rho_{\text{solid}}+\phi\sum_{\ell=1}^{np}\rho_{\ell}s_{\ell}$$

as mixture density or bulk density, and be consistent everywhere.

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We should decide whether we want to refer to the expression:

ρ = ( 1 − ϕ ) ρ solid + ϕ ∑ c ρ c = ( 1 − ϕ ) ρ solid + ϕ ∑ c ∑ ℓ = 1 n p x c ℓ ρ ℓ s ℓ = ( 1 − ϕ ) ρ solid + ϕ ∑ ℓ = 1 n p ρ ℓ s ℓ

as mixture density or bulk density, and be consistent everywhere.

can we call this totalDensity instead of bulk density ? ? It's certainly not the mixture density.

We should decide whether we want to refer to the expression:
ρ = ( 1 − ϕ ) ρ solid + ϕ ∑ c ρ c = ( 1 − ϕ ) ρ solid + ϕ ∑ c ∑ ℓ = 1 n p x c ℓ ρ ℓ s ℓ = ( 1 − ϕ ) ρ solid + ϕ ∑ ℓ = 1 n p ρ ℓ s ℓ
as mixture density or bulk density, and be consistent everywhere.

can we call this totalDensity instead of bulk density ? ? It's certainly not the mixture density.

Looking at the code, IMO, what we call totalMassDensity should be called mixtureDensity and the totalDensity should include the solid part.

We should decide whether we want to refer to the expression:
ρ = ( 1 − ϕ ) ρ solid + ϕ ∑ c ρ c = ( 1 − ϕ ) ρ solid + ϕ ∑ c ∑ ℓ = 1 n p x c ℓ ρ ℓ s ℓ = ( 1 − ϕ ) ρ solid + ϕ ∑ ℓ = 1 n p ρ ℓ s ℓ
as mixture density or bulk density, and be consistent everywhere.

can we call this totalDensity instead of bulk density ? ? It's certainly not the mixture density.

Looking at the code, IMO, what we call totalMassDensity should be called mixtureDensity and the totalDensity should include the solid part.

I agree it is confusing. Often, in the poromechanics literature authors refer to mixture including the solid phase, for example: "... a three-phase mixture composed of a solid matrix whose voids are continuous and filled
with water and air ..." [Borja, CMAME (2004)].

In my opinion, we should agree on consistent naming for:

• solid phase(s)
• fluid phases and their mixture
• solid/fluid combined

Also the notation used in the documentation should be updated accordingly.

We should decide whether we want to refer to the expression:
ρ = ( 1 − ϕ ) ρ solid + ϕ ∑ c ρ c = ( 1 − ϕ ) ρ solid + ϕ ∑ c ∑ ℓ = 1 n p x c ℓ ρ ℓ s ℓ = ( 1 − ϕ ) ρ solid + ϕ ∑ ℓ = 1 n p ρ ℓ s ℓ
as mixture density or bulk density, and be consistent everywhere.

can we call this totalDensity instead of bulk density ? ? It's certainly not the mixture density.

Looking at the code, IMO, what we call totalMassDensity should be called mixtureDensity and the totalDensity should include the solid part.

I agree it is confusing. Often, in the poromechanics literature authors refer to mixture including the solid phase, for example: "... a three-phase mixture composed of a solid matrix whose voids are continuous and filled with water and air ..." [Borja, CMAME (2004)].

In my opinion, we should agree on consistent naming for:

* solid phase(s)

* fluid phases and their mixture

* solid/fluid combined

Also the notation used in the documentation should be updated accordingly.

I mean, I think the definition of mixture is quite broad so technically one could see the solid + fluids as a mixture. However, since we are often interested in the properties of just the fluid mixture I think that it is more straightforward to call:

• mixture or fluidMixture the mixture of the fluid phases and so refer to the mixtureDensity or the fluidMixtureDensity for that one.
• totalDensity the density of the fluidMixture plus the solid. And I d do the same thing with energy, enthalpy etc.
  Mainly coz it's weird to have something called totalDensity that does not include all phases present.

• totalDensity the density of the fluidMixture plus the solid. And I d do the same thing with energy, enthalpy etc.
  Mainly coz it's weird to have something called totalDensity that does not include all phases present.

i would say totalDensity is kind of reserved for fluid total density

• totalDensity the density of the fluidMixture plus the solid. And I d do the same thing with energy, enthalpy etc.
  Mainly coz it's weird to have something called totalDensity that does not include all phases present.

i would say totalDensity is kind of reserved for fluid total density

yeah, I actually don't like the name totalDensity for the fluid mixture one. But at the end of the day as long as we are consistent, it's fine.