To correct error in the documentation of component transport processes
There is an error in the equation defining the "hydrodynamic dispersion tensor" included in component transport processes "HC".
The tortuosity tensor multiplying the molecular diffusion coefficient is missing --> Which means that what we actually need to include in OGS at the present moment is the "pore-diffusion coefficient" and not the "molecular diffusion coefficient" (diffusion in "free water").
Note: To have the correct nomenclature for the diffusion coefficient is quite important to avoid errors in pure diffusive fluxes normally controlling mass transport in low permeable media (i.e. clays)
Next steps
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To change the nomenclature on the code from "molecular diffusion coefficient" to "pore diffusion coefficient"
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To change the pdf document describing the equation system--> https://www.opengeosys.org/docs/benchmarks/hydro-component/hydro-component/ --> Equation 1.17
Note
This modification does not have any implication in the equation system implemented in OGS but avoid conceptual errors when modelling "pure diffusive systems". As discussed in !3191 (merged) --> Molecular diffusion coefficients in water are in the range of 10-9 m2/s, pore diffusion coefficients can be 1 or 2 orders of magnitude lower.