non convergence with langmuir adsortion parameters

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Posts: 5
Joined: Mon Jul 13, 2020 3:35 am
Location: Colombia

non convergence with langmuir adsortion parameters

Post by jorge.antia » Fri Jul 24, 2020 6:25 pm


the issue is that we get the message

"Does not converge in the solute transport module ! Check iteration criteria in the Solute Transport - General Information window!"

in that window we especified the following, acording with the manual we had this input for iteration criteria

Abolute conc tolerance: 0.001
relative conc tolerance: 0.001
max numb of iterations: 10

the former, for a 4 layer vadose zone, in wich the solute has the following langmuir parameters:

kd cm3/mg nu cm3/mg
0.5 14.811
0.87953 10.04
0.70705 10.04
2.7862 0.5

we have run the program with all the above reaction parameters equal to 1, and works perfect, so please, if you have any advice we`d be gratefull

thank you in advance for any help

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Location: Riverside, CA

Re: non convergence with langmuir adsortion parameters

Post by Jirka » Fri Jul 24, 2020 6:56 pm

HYDRUS may not be able to solve this as these are very nonlinear functions (see the differences in slopes at low and large concentrations), with orders of magnitude differences in the max sorbed concentrations (which does not seem very realistic). You need to try different iteration criteria (likely higher relative tolerance) and smaller time steps. J.
Langmuir.png (7.53 KiB) Viewed 504 times

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