OGS-Phreeqc reaction not occurring in the entire domain

Hi,

I am facing a problem. Can anyone please help me out with this ?

It is a simple groundwater flow and mass transport problem with OGS-PhreeqC. (it is a 0.5m 1D domain)

The two attached input files are same except :

  1. in initial condition file no boundary condition has been set for the reactants, only initial concentrations of 20 mol/kg has been provided for the reactants at point0. Here in the output file (pds_domain_line.tec) I can see that the entire domain is filled with the reactants and the product (calcite) after a certain time.

  2. in the boundary condition file, I have set the initial concentration as 20 mol/kg and the boundary concentration as 5 mol/kg at point0. But in the output file (pds_domain_line.tec), I see that though the entire domain is filled with reactants, the reaction is taking place only in the first 10 cm (even if I increase the time and concentration, there is no effect). I want the reaction to take place in the entire domain.

Could you please help me to find out where I am wrong? (sorry for my bad concept in modeling)

Thank you so much for your time and help.

Sincerely,

Sumana Bhattacharya

OGS_PhreeqC_reaction_issue.zip (2.47 MB)

Dear Sumana,
please check the phinp.out file, which shows detailed phreeqc output for the reactions at each grid node:

...

Beginning of initial solution calculations.

···

-------------------------------------------

Initial solution 7.

WARNING: Maximum iterations exceeded, 100

WARNING: Maximum iterations exceeded, 100

WARNING: The program has failed to converge to a numerical solution.

The following equations were not satisfied:
ERROR: C(4) has not converged. Total: 4.967901e+00 Calculated: 2.137134e+00 Residual: 2.830767e+00

ERROR: Ca has not converged. Total: 4.967901e+00 Calculated: 2.418773e+00 Residual: 2.549128e+00

ERROR: H(1) Charge balance has not converged. Residual: -5.639697e-01

ERROR: A(H2O) Activity of water has not converged. Residual: 1.605228e+01

-----------------------------Solution composition------------------------------

  Elements Molality Moles

  C(4) 2.137e+00 2.137e+00
  Ca 2.419e+00 2.419e+00

----------------------------Description of solution----------------------------

                                        pH = 12.032 Charge balance
                                        pe = 11.370

...

ERROR: Model failed to converge for initial solution 7.

Stopping.

Phreeqc quits at the 7th grid node, so there probably is something fatally wrong in your model setup.

Best regards, Christof

Am 27.04.2015 um 08:08 schrieb sumanab24:

Hi,

I am facing a problem. Can anyone please help me out with this ?

It is a simple groundwater flow and mass transport problem with
OGS-PhreeqC. (it is a 0.5m 1D domain)

The two attached input files are same except :

1) in initial condition file no boundary condition has been set for the
reactants, only initial concentrations of 20 mol/kg has been provided
for the reactants at point0. Here in the output file
(pds_domain_line.tec) I can see that the entire domain is filled with
the reactants and the product (calcite) after a certain time.

2) in the boundary condition file, I have set the initial concentration
as 20 mol/kg and the boundary concentration as 5 mol/kg at point0. But
in the output file (pds_domain_line.tec), I see that though the entire
domain is filled with reactants, the reaction is taking place only in
the first 10 cm (even if I increase the time and concentration, there is
no effect). I want the reaction to take place in the entire domain.

Could you please help me to find out where I am wrong? (sorry for my bad
concept in modeling)

Thank you so much for your time and help.
Sincerely,
Sumana Bhattacharya

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_______________________________________
Dr. Christof Beyer
Institute of Geosciences
Geohydromodelling
Christian-Albrechts-University Kiel
Ludewig-Meyn-Str. 10
24118 Kiel
Germany

phone: +49(0)431-8803172
fax: +49(0)431-8807606
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_______________________________________