M. W. Guidry, J. J. Billings, W. R. Hix
In two preceding papers we have shown that, when reaction networks are
well-removed from equilibrium, explicit asymptotic and quasi-steady-state
approximations can give algebraically-stabilized integration schemes that rival
standard implicit methods in accuracy and speed for extremely stiff systems.
However, we also showed that these explicit methods remain accurate but are no
longer competitive in speed as the network approaches equilibrium. In this
paper we analyze this failure and show that it is associated with the presence
of fast equilibration timescales that neither asymptotic nor quasi-steady-state
approximations are able to remove efficiently from the numerical integration.
Based on this understanding, we develop a partial equilibrium method to deal
effectively with the approach to equilibrium and show that explicit asymptotic
methods, combined with the new partial equilibrium methods, give an integration
scheme that plausibly can deal with the stiffest networks, even in the approach
to equilibrium, with accuracy and speed competitive with that of implicit
methods. Thus we demonstrate that such explicit methods may offer alternatives
to implicit integration of even extremely stiff systems, and that these methods
may permit integration of much larger networks than have been possible before
in a number of fields.
View original:
http://arxiv.org/abs/1112.4738
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