Abstract
The numerical simulation of flow and reactive transport in porous media with complex domains is nontrivial. This paper presents a method to implement fully unstructured grid capabilities into the well-established software ParMIN3P-THCm, a process-based numerical model designed for the investigation of subsurface fluid flow and multicomponent reactive transport in variably saturated porous media with parallelization capability. The enhanced code, MIN3P-HPC, is modularized to support different cell types, spatial discretization methods and gradient reconstruction methods. MIN3P-HPC uses a vertex-centered control volume method with consideration of both vertex-based and cell-based material properties (e.g., permeability). A flexible parallelization scheme based on domain decomposition and thread acceleration was implemented, which allows the use of OpenMP, MPI and hybrid MPI-OpenMP, making optimized use of computer resources ranging from desktop PCs to distributed memory supercomputers. The code was verified by comparing the results obtained with the unstructured grid version to those produced by the structured grid version. Numerical accuracy was also verified against analytical solutions for 2D and 3D solute transport, and by comparison with third-party software using different cell types. Parallel efficiency of OpenMP, MPI and hybrid MPI-OpenMP versions was examined through a series of solute transport and reactive transport test cases. The results demonstrate the versatility and enhanced performance of MIN3P-HPC for reactive transport simulation.
Highlights
Numerical models for subsurface flow and reactive transport have become important tools in helping researchers and engineers to gain a better understanding of physical, chemical and biological processes in the field of earth and environmental sciences
Many advances have been made in recent years, and the field of reactive transport modeling has matured to a degree that allows for application of these models on a larger scale, requiring the consideration of more complex geometry
This paper introduced the implementation of unstructured grid capabilities into the existing reactive transport codes MIN3P-THCm and ParMIN3P-THCm
Summary
Numerical models for subsurface flow and reactive transport have become important tools in helping researchers and engineers to gain a better understanding of physical, chemical and biological processes in the field of earth and environmental sciences. Due to the relative complexity of the numerical algorithms, capabilities for simulating reactive transport using unstructured grids are not well developed This is in part because unstructured grid techniques generate increased computational overhead compared to structured grid methods, a fact that has limited their use for large 3D simulations (Mavriplis 1997). The enhanced code is named MIN3P-HPC, where HPC stands for high-performance computing as well as high-performance code for complex geometry The objectives of this contribution are to present (1) the development of a flexible method supporting different cell types in 2D and 3D, while maintaining high-order numerical accuracy; and (2) the implementation of a high-performance parallelization approach that takes advantage of cutting-edge computer architecture, and allows the use of OpenMP, MPI or hybrid MPI-OpenMP for acceleration and scaling
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