ICs, BCs, fixes

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Marco De Lucia 2023-08-26 14:24:26 +02:00
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@ -29,61 +29,105 @@ mpirun -np 4 ./poet --interp barite_interp_eval.R barite_results
The benchmark depicts an isotherm porous system at *25 °C* where pure
water is initially at equilibrium with *celestite* (strontium sulfate;
brute formula: SrSO_4).
A solution containing only dissolved Ba^{2+} and Cl^- diffuses into
the system causing celestite dissolution. The increased concentration
of dissolved sulfate SO_{4}^{2-} induces precipitation of *barite*
(barium sulfate; brute formula: BaSO_{4}^{2-}). The overall reaction
can be written:
brute formula: SrSO_{4}). A solution containing only dissolved Ba^{2+}
and Cl^- diffuses into the system causing celestite dissolution. The
increased concentration of dissolved sulfate SO_{4}^{2-} induces
precipitation of *barite* (barium sulfate; brute formula:
BaSO_{4}^{2-}). The overall reaction can be written:
Ba^{2+} + celestite \rightarrow barite + Sr^{2+}
Both celestite dissolution and barite precipitation are calculated
using a kinetics rate law based on transition state theory:
rate = -S_{m} K (1-SR_{m})
rate = -S_{m} k_{barite} (1-SR_{m})
where the reaction rate has units mol/s, S_{m} (m^{2}) is the reactive
surface area, K (mol/m^{2}/s) is the rate constant, and SR is the
saturation ratio, i.e., the ratio of the ion activity product of the
reacting species and the solubility constant.
surface area, k (mol/m^{2}/s) is the kinetic coefficient, and SR is
the saturation ratio, i.e., the ratio of the ion activity product of
the reacting species and the solubility constant, calculated
internally by PHREEQC from the speciated solution.
For barite, the reaction rate is computed as sum of two mechanisms,
r_{/acid/} and r_{/neutral/}:
rate_{barite} = S_{barite} (r_{/acid/} + r_{/neutral/}) * (1 - SR_{barite})
rate_{barite} = S_{barite} (k_{/acid/} + k_{/neutral/}) * (1 - SR_{barite})
where:
r_{/acid/} = 10^{-6.9} e^{-30800 / R} \cdot act(H^{+})^{0.22}
k_{/acid/} = 10^{-6.9} e^{-30800 / R} \cdot act(H^{+})^{0.22}
r_{/neutral/} = 10^{-7.9} e^{-30800 / R}
k_{/neutral/} = 10^{-7.9} e^{-30800 / R}
R (8.314462 J K^{-1} mol^{-1}) is the gas constant.
For celestite the kinetic law considers only the acidic term and
For celestite the kinetic law considers only the acidic mechanism and
reads:
rate_{celestite} = S_{celestite} 10^{-5.66} e^{-23800 / R} \cdot
act(H^{+})^{0.109} \cdot (1 - SR_{celestite})
The kinetic rate laws as implemented in the =db_barite.dat= file
accepts one parameter which represents reactive surface area in m^{2}.
For the benchmarks the surface areas are set to
The kinetic rates as implemented in the =db_barite.dat= file accepts
one parameter which represents reactive surface area in m^{2}. For the
benchmarks the surface areas are set to
- S_{barite}: 50 m^{2}
- S_{celestite}: 10 m^{2}
A starting seed for barite is given at 0.001 mol in each domain
element.
** Initial conditions
* TODO Nucleation
The parametrization
Geochemical benchmark inspired by Tranter et al. (2021) without
nucleation.
* POET simulations
Currently these benchmarks are pure diffusion simulations. There are 7
transported species: H, O, Charge, Ba, Cl, S(6), Sr.
** =barite.R=
- Grid discretization: square domain of 1 \cdot 1 m^{2} discretized in
20x20 cells
- Boundary conditions: E, S and W sides of the domain are closed; the
N boundary has a *fixed concentration* (Dirichlet) of 0.1 molal
BaCl_{2}
- Diffusion coefficients: isotropic homogeneous \alpha = 1E-06
- Time steps & iterations: 20 iteration with \Delta t = 250 s
- *DHT* parameters:
| H | 10 |
| O | 10 |
| Charge | 3 |
| Ba | 5 |
| Cl | 5 |
| S(6) | 5 |
| Sr | 5 |
** =barite_interp_eval.R=
- Grid discretization: rectangular domain of 40 \cdot 20 m^{2}
discretized in 400 \cdot 200 cells
- Boundary conditions: all boundaries are closed. The center of the
domain at indeces (200, 100) has fixed concentration of 0.1 molal of
BaCl_{2}
- Diffusion coefficients: isotropic homogeneous \alpha = 1E-06
- Time steps & iterations: 200 iterations with \Delta t = 250 s
- *PHT* parameters:
| H | 10 |
| O | 10 |
| Charge | 3 |
| Ba | 5 |
| Cl | 5 |
| S(6) | 5 |
| Sr | 5 |
* References
- Tranter, Wetzel, De Lucia and Kühn (2021): Reactive transport model
of kinetically controlled celestite to barite replacement, Adv.
Geosci., 1, 19 ,https://doi.org/10.5194/adgeo-1-1-2021
of kinetically controlled celestite to barite replacement, Advances
in Geosciences, 1, 19, https://doi.org/10.5194/adgeo-1-1-2021