Density term missing in 1D continuity equation?

[Mohamad Fathi]

Hi there,

I was checking the governing equations for the one-dimensional flow formulation and noticed that the continuity equation seems to be missing the density term in the z-derivative. It’s written as:
    ∂u/∂z + 2ρV = 0
while I think it should be:
    ∂(ρu)/∂z + 2ρV = 0.

Could you please confirm whether the solver uses the correct form?

Best wishes,
Mohamad

[Thorsten Zirwes]

I think you are right: in the governing equations section, density is missing:

https://cantera.org/stable/reference/onedim/governing-equations.html#axisymmetric-stagnation-flow

But in the discretization section, it is written correctly:

https://cantera.org/stable/reference/onedim/discretization.html#continuity-equation

Also the code treats this correctly:

https://github.com/Cantera/cantera/blob/main/src/oneD/Flow1D.cpp#L541-L542