Convergence problem in initialization of water composition
Hello, everyone,
When I run my TOUGHREACT model, the runlog.out file displayed "ERROR (convergence problem in initialization of water composition) Please adjust convergence criteria regarding chemical iteration and initial guess of concentration of primary species".
The TOUGHREACT v2.0 manual gives: "Execution stop: yes. Self-explanatory. This error results in calling routine chdump for troubleshooting (i.e. the last chemical speciation data are output in the chdump.out file). This error occurs during the initial geochemical speciation of waters specified in chemical.inp (no minerals, before the first time step). Check the chdump.out file for clues, and also check that water temperatures specified in chemical.inp data are not too different than the initial condition of temperature specified in the flow.inp file."
I am confused by the statements. I was wondering if there were something wrong in my initial water conditions (Actually, I changed the temperatures and the initial concentrations for many times based on the equilibrium constant) and how to revise it.
Thank you!
2 replies
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Hi Lang,
Yes, those messages are a little verbose. 90% of the time the problem is in your initial guess concentration for species that are not close to the total concentration. Usually, you must reduce the guess for species such as Al+3, Fe+2, or O2(aq), by many orders of magnitude. Keep modifying the guesses for species that may be way off, and usually it will converge. Usually Cl, Na, K, Ca, etc. (nonredox species) have guesses close enough to ctot. Leave the number of maximum number of chemical iterations alone (should be 200-300)., and the convergence criteria (1e-5 or 1e-6). Changing those rarely helps, and it is not a good idea to make them too large. If you have more trouble send me the chemical inputs.
regards,
Eric
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Dear Dr. Eric Sonnenthal,
Thank you so much for your helpful answer.
Best regards,
Lang