Reconciling Flow and Chemical Inputs
I have a couple questions that are very basic and therefore hopefully rather straightforward for someone to answer. I am just getting started using TOUGHREACT, and I can't tell from the reading I've done how some pieces of information are shared among the various components of a reactive transport simulation. I am using ECO2N, so I will use that as an example as I pose my question, which is outlined in two sections below:
- How does the code "choose" between the various ways that chemical concentrations must be provided as inputs? In ECO2N, mass fractions of salt and CO2 must be included when defining initial conditions in flow.inp, but then concentrations of h+, hco3-, na+, and cl- must also be defined in chemical.inp. Which of these seemingly redundant definitions will the code honor when it runs the simulation? It seems easiest to input the chemistry through chemical.inp, but then what should I do about the XCO2 and Xsalt parts of the initial conditions that I define in flow.inp?
- How does the code reconcile the spatial components of flow.inp and chemical.inp? That is, how can I use chemical.inp to define the spatial extent of a part of the model that has different chemical composition than the rest of the domain, and make sure that it corresponds to the correct area within my flow simulation (i.e., a subsection of the elements defined in the ELEME block of flow.inp)?
Thank you very much in advance for your assistance,
1. The chemical and flow equations are not solved simultaneously, but sequentially. So what you define in flow.inp will be used to account for flow transport (including, in this case, salt dissolution and precipitation and thermophysical-property changes incurred by changes of CO2, water, and salt concentrations in the fluids), whereas the inputs provided in chemical.inp dictate how chemical reactions will take place. You're right that the two processes should (and do) interact with one another, and I can't say I completely understand how that plays out with ECO2N, where there are seemingly overlapping phenomena that are supposed to be accounted for in both flow and chemical processes. I'll leave it for someone else like Eric Sonnenthal or Nic to answer more completely.
2. Look at Record_12 of solute.inp from the TOUGHREACT Manual (pg. 22). You can list out the elements associated with a particular mineral, water chemistry, etc. I believe Eric Sonnenthal may have included the ability to choose based also on material type in the ROCKS block, but I don't know if that capability's been incorporated into any of the released version. Again, I'll leave it for the developers to answer.
Hope that helps, even if I didn't answer your questions fully.