diff --git a/bench/barite/README.org b/bench/barite/README.org index 589ca25a7..6378516b5 100644 --- a/bench/barite/README.org +++ b/bench/barite/README.org @@ -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, 1–9 ,https://doi.org/10.5194/adgeo-1-1-2021 + of kinetically controlled celestite to barite replacement, Advances + in Geosciences, 1, 1–9, https://doi.org/10.5194/adgeo-1-1-2021