Application of Flux Corrected Transport for Multicomponent Reactive Transport Modeling
نویسندگان
چکیده
Reactive transport describes the coupling among flow, transport and chemical reactions occurring in porous media; and therefore it is important in areas such as aquifer remediation, groundwater contamination, geochemical reaction modeling and CO2 sequestration. Due to the large time scales involved and/or the lack of accessibility to the subsurface, in most of these studies an adequate representation of the important physical and chemical processes require numerical simulation. Conventional numerical methods to solve the reactive transport equations can produce nonphysical values (negative concentrations), particularly for cases with highly heterogeneous flow fields, irregular grids and full tensor dispersion. Negative concentrations can cause numerical convergence problems and therefore cannot be tolerated, specially when transport is coupled to nonlinear reactions. These problems can be solved using a methodology called flux corrected transport, in which a positive solution can be obtained combining a high-order solution (high accuracy but non-positive) and a low-order solution (positive but dispersive). The numerical dispersion of the low-order solution is corrected using an antidiffusion component obtained from high-order solution in order to improve its accuracy. In regions of non-physical values, the low-order solution predominates while the high-order solution is prevalent in the areas of sharp changes. In this study, flux corrected transport is tested in reactive transport problems with spatial variability and diagonal flow, and the results indicate that this is a simple and flexible method to obtain a positive solution in a reactive transport framework. This methodology can be easily adapted to existing discretizations, therefore there is no need to extensively modify existing codes.
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