dual porosity conc. flux bc

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lea.augustin
Posts: 1
Joined: Fri Apr 30, 2021 10:01 am
Location: Germany

dual porosity conc. flux bc

Post by lea.augustin » Fri Apr 30, 2021 10:37 am

Hello,

We are currently modelling water flow and mass transport in two lysimeters. For solute transport we have chosen the upper boundary condition 'concentration flux' to control the mass balance. With the single porosity approach this works quite well, as the precipitation times our solute input determines the concentration flux at the upper boundary. When switching to dual porosity, the modelled concentration flux becomes larger (10 to 15%) with the same input values. Could you explain why this happens and how to quantify the change?
Also, the concentration flux and the cumulative concentration flux given in the solute.out file no longer match, but the cumulative concentration flux ('sum(cvtop)') is greater than the sum of the individual concentration fluxes from the first column ('cvtop').

Thank you in advance and kind regards,
Lea

Jirka
Posts: 5216
Joined: Sat Mar 16, 2002 3:47 pm
Location: USA
Location: Riverside, CA

Re: dual porosity conc. flux bc

Post by Jirka » Fri Apr 30, 2021 8:25 pm

1. I do not see how this could happen, unless you use the Concentration BC at the upper surface, which is almost always physically incorrect.
2. 'sum(cvtop)' is not the sum of the individual concentration fluxes from the first column ('cvtop'), but its integration over time.

J.

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