Effects of chemical reactions on iterative methods for implicit time stepping

We compare the performance of the fully coupled Newton-Raphson method with the sequential iteration approach (SIA) for solving the implicit time stepp ing equations of reactive transport modeling. We formulate the implicit tim e stepping equations for a demonstration model that incorporates homogeneou s equilibrium reactions, i.e. carbonate hydrolysis, and a heterogeneous equ ilibrium reaction, i.e. the dissolution/precipitation of calcite. The demon stration model uses a coupled pair of mixing cells as a simplified form of transport. The effects of the homogeneous and heterogeneous reactions on th e iterative methods are demonstrated. (C) 1998 Elsevier Science Limited. Al l rights reserved.