Algorithms for activity correction models for reactive transport.
Reactive transport codes are very useful elements of environmental
research. They now contain multiphysics with very complex algorithms,
including flow, transport, chemical and sometimes heat transport,
mechanical and/or biological algorithms. Because of this complexity,
some parts of these algorithms still have not been sufficiently studied.
Here, we present a comparison of 3 algorithms for activity correction, a
specific subset of equilibrium chemistry algorithms. We show that the
most used algorithm (the inner fixed-point algorithm) or the most
rigorous algorithm (the full Newton) might not be the most efficient,
and we propose the outer fixed-point algorithm, which is more robust and
faster than other algorithms.