Re: PHREEQC problem

["David L Parkhurst" <dlpark@xxxxxxxx>]

I have been working on a method for integrating the rate equations that
works better with stiff equations. I have implemented a package called
CVODE from Lawrence Livermore National Lab as an alternative to the
Runge-Kutta method that should speed up the calculations. This version
should work better when you are trying to simulate equilibrium by using
fast rates, which is the situation in the problem you sent me earlier. You
should be able to use the enclosed version without having to increase the
rate constants to be on the order of the time step. I have done some
preliminary testing and the program seems to work, but you should do some
additional testing to make sure it is working correctly on your problems.
The enclosed program has identical functionality to PHREEQC, except this
version uses CVODE to integrate rate expressions, which could be slower
than RK in some (many?) cases. Please let me know if you find any bugs and,
if you use it, whether it works satisfactorily.

David

(See attached file: phreeqc.cvode.exe)


David Parkhurst (dlpark@xxxxxxxx)
U.S. Geological Survey
Box 25046, MS 413
Denver Federal Center
Denver, CO 80225

Project web page: https://wwwbrr.cr.usgs.gov/projects/GWC_coupled

Attachment: phreeqc.cvode.exe
Description: Binary data