Numerical methods for reactive transport on rectangular and streamline-oriented grids

Coupling advection-dominated transport to reactive processes leads to addit ional requirements and limitations for numerical simulation beyond those fo r non-reactive transport. Particularly, both monotonicity avoiding the occu rence of negative concentrations, and high-order accuracy suppressing artif icial diffusion, are necessary to study accurately the reactive interaction s of compounds transported in groundwater. These requirements are met by no n-linear Eulerian methods. Two cell-centered Finite Volume schemes are pres ented for the simulation of advection-dominated reactive transport. The fir st scheme is based on rectangular grids, whereas the second scheme requires streamline-oriented grids the generation of which is explained in an accom panying paper. Although excellent results for conservative transport are ob tained by the scheme for rectangular grids, some artificial transverse mixi ng occurs in the case of multi-component transport. This may lead to errone ous reaction rates if the compounds interact. The transport scheme for stre amline-oriented grids, on the other hand, avoids artificial transverse mixi ng. A quantitative comparison is given by two test cases. A conservative tr acer simulation for a five-spot configuration in a heterogeneous aquifer sh ows a high coincidence of the breakthrough curves obtained for the two meth ods, whereas a test case of two reacting compounds shows significant differ ences. In this test case, a rate of convergence with respect to the overall reaction rates lower than first-order is calculated for the rectangular gr id. (C) 1999 Elsevier Science Ltd. All rights reserved.