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Problem at the boundary condition/Reactive transport modelling
Posted 13 juin 2022, 15:39 UTC−4 Geomechanics, Chemical Reaction Engineering Version 5.6 2 Replies
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Hello Everyone, I am new to the COMSOL so i need a bit help here. I am modeling diffusion advection case with simple 1D. I try to simulate the injection of CO2. I am using "Transport of Diluted Species in Porous Media (tds)" in comosl 5.6. I have introduced following chemical equilibrium reactions with appropriate constant of equilibrium values for each reaction. This simulates the dissoultion of CaCO3 as result of CO2 injection.
- H2O = H+ +OH-
- CO2 (aq) + H2O = H+ + HCO3-
- HCO3- = H+ +CO3 2-
- CaCO3 = Ca2+ + CO3 2-
the boundary conditions are "inflow" at the inlet where I inject CO2 with 100 mol/m^3 and “No flux” condition at the outlet (advection not included). I have a constant velocity of 1e-8 m/s and diffusion coefficient for all the species is equal to 1e-9 m^2/s. (No adsorption or dispersion) .
When I run the model I get satisfactory results. **The only problem is, when I check the total fluxes for different species at the inlet I get a non-zero value. In rules as I am injecting only CO2 I should not get any other inflows. **
I have attached the initial values and the total fluxes for CO2 and Ca++ at the inlet. ‘Line 1’ is for inlet and ‘Line 11’ is for outlet.
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Perhaps you have to explicitly define that the inflow of other species is zero.
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yes the inflow of other species is zero. see the attached photo.
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