Development of an isotopic fractionation and filiation module in the reactive transport code HYTEC

International audienceThe increasing place of numerical modelling in the geosciences, as in numerous fields is well known. Owing to rapid progress in computer sciences and hardware, more and more complex systems, i.e. also more and more realistic ones, can be simulated. HYTEC is a versatile coupled reactive transport code, currently used for several applications, such as groundwater pollution studies, safety assessment of nuclear waste disposals, CO2 storage, geochemical studies or interpretation of laboratory column experiments. This work presents a newly developed functionality in HYTEC, which allows taking into account isotopic speciation and filiation. Variations in isotopic compositions give useful information for the geosciences. They can help track the evolution of aqueous and mineral species, mixing of different origin fluids, and are helpful for dating. Then, environmental isotopes experiences and modelling complete geochemical and physical hydrology studies

Comparison of numerical methods for simulating strongly non-linear and heterogeneous reactive transport problems – the MoMaS benchmark case

International audienceAlthough multicomponent reactive transport modeling is gaining wider application in various geoscience fields, it continues to present significant mathematical and computational challenges. There is a need to solve and compare the solutions to complex benchmark problems, using a variety of codes, because such intercomparisons can reveal promising numerical solution approaches and increase confidence in the application of reactive transport codes. In this contribution, the results and performance of five current reactive transport codes are compared for the 1D and 2D sub-problems of the so-called "Easy Test Case" of the MoMaS benchmark (Carrayrou et al., this issue). As a group, the codes include iterative and non-iterative operator splitting, and global implicit solution approaches. The 1D Easy Advective and 1D Easy Diffusive scenarios were solved using all codes and, in general, there was good agreement, with solution discrepancies limited to regions with rapid concentration changes. Computational demands were typically consistent with what was expected for the various solution approaches. The most important outcome of the benchmark exercise is that all codes are able to generate comparable results for problems of significant complexity and computational difficulty

Numerical Results with a Global Method for 2D Reactive Transport Problems,

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Analysis of Numerical Methods for Coupling Transport Andgeochemistry Equations

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Isotopic management in the reactive transport code hytec: isotopic fractionation and radioactive decay

International audienc

A global approach to reactive transport: application to the MoMas benchmark

International audienceWater resource management involves numerical simulations in order to study contamination of groundwater by chemical species. Not only do the aqueous components move due to physical advection and dispersion processes, but they also react together and with fixed components. Therefore the mass balance couples transport and chemistry, and reactive transport models are PDEs coupled with nonlinear algebraic equations. In this paper, we present a global method based on the method of lines and DAE solvers. At each time step, nonlinear systems are solved by a Newton- LU method. We use this method to carry out numerical simulations for the reactive transport benchmark proposed by the MoMas research group. Although we study only 1D computations with a specific geochemical system, several difficulties arise. Numerical experiments show that our method can solve quite difficult problems, get accurate results and capture sharp fronts

Numerical Results with a Global Method for 2D Reactive Transport Problems,

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A global strategy for solving reactive transport equations

http://www.sciencedirect.com/science/article/B6WHY-4WGDR6C-1/2/ada7965dcd6096984365876b64411966International audienceReactive transport models are complex nonlinear Partial Differential Algebraic Equations (PDAE), coupling the transport engine with the geochemical operator. We propose an efficient and robust global numerical method, based on a method of lines and Differential Algebraic Equations (DAE) solvers, combined with a Newton method using a powerful sparse linear solver. Numerical experiments show the performances of the method. We also propose a unified framework to describe classical methods such as Sequential Non-Iterative Approach, Sequential Iterative Approach, Direct Substitution Approach and compare them with our global metho