Clausnitzer at al comparing meshing approaches
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This document compares layered and unstructured tetrahedral meshing approaches for groundwater modeling at a geometrically complex mine site. It finds that fully unstructured tetrahedral meshing can substantially reduce mesh size while maintaining geologic detail. This allows direct solvers to be applied, improving simulation performance. Specifically, a tetrahedral mesh reduced nodes from over 2.8 million to under 200,000, decreasing solution times from over 1000 seconds to under 22 seconds compared to the legacy layered meshing approach.
Clausnitzer at al comparing meshing approaches
- 1. Comparing meshing approaches for groundwater modeling at a geometrically challenging mine site Volker Clausnitzer, Fabien Cornaton, Peter Sch辰tzl DHI-WASY Robin Dufour DHI Peru
- 3. Legacy layered meshing 息 DHI #3 18 geological formations 85 numerical layers 10 million elements 5 million nodes 18 geological formations 85 numerical layers continuous, following the faults 10 million elements 5 million nodes
- 4. Mesh Flexibility in 3D 息 DHI Layered prism-based FE meshes Excellent flexibility in 2D Extruded to 3D Vertical join faces restrict flexibility but simplify interactive model set-up once mesh has been created Unstructured tetrahedral FE meshes Excellent flexibility in 3D Difficult to handle in interactive work
- 5. 3D element types 息 DHI Layered meshes Penta- or hexahedrons with vertical quadrilateral join faces
- 6. 3D element types 息 DHI Unstructured meshes / mesh parts Tetrahedrons
- 7. 3D element types 息 DHI Combined meshes Pyramids connect layered and unstructured mesh portions
- 8. TetGen 息 DHI Mesh generator for tetrahedral meshing of any 3D polyhedral domain Author: Hang Si (Weierstrass Institute for Applied Analysis and Stochastics, WIAS Berlin) tetgen.org
- 9. Tetrahedral meshing embedded in a layered mesh 息 DHI
- 10. Embedded tetrahedral mesh 息 DHI Strategy: Combine mesh types Where possible, mesh with layered prisms Where necessary, embed unstructured tetrahedral meshes (artificial underground structures, inclined faults karstic networks, pinch-outs, )
- 11. Embedded tetrahedral mesh: Karstic network 息 DHI
- 12. Embedded tetrahedral mesh: Karstic network 息 DHI
- 13. Embedded tetrahedral mesh: Karstic network 息 DHI
- 14. Fully unstructured tetrahedral meshing 息 DHI
- 15. Legacy Approach 息 DHI 3D GeoModeller geologic model Layered-mesh FEFLOW model
- 16. 息 DHI Steady-state solution 22 layers; 5,380,760 pentahedral elements; 2,816,304 nodes
- 17. Fully unstructured (tetrahedral) meshing 息 DHI Takes spatial distribution of geologic units, 3D geometric description of unit interfaces from dedicated geologic modelers 3D GeoModeller, GOCAD, (Leapfrog, MineSight, ) Geometric constraints passed to TetGen GUI-supported parameter assignment based on geologic spatial information
- 18. 息 DHI Interfaces of geologic units
- 19. 息 DHI Interfaces and geologic units
- 20. 息 DHI Interfaces and geologic units
- 21. 息 DHI Tet-meshed geologic units
- 23. 息 DHI Full tetrahedral mesh
- 24. 息 DHI Steady-state solution 861,685 tetrahedral elements; 195,628 nodes
- 26. 息 DHI 6 cores
- 27. Performance Comparison 息 DHI Layered Mesh Tetrahedral Mesh Number of nodes (Size of equation system) 2,816,304 195,628 SAMG Algebraic Multigrid Solver Simulation time (seconds) 654.67 18.95 PARDISO Parallel Direct Solver Simulation time (seconds) 1104.62 21.73
- 28. Performance Comparison 息 DHI Layered Mesh Tetrahedral Mesh Number of nodes (Size of equation system) 2,816,304 195,628 SAMG Algebraic Multigrid Solver Simulation time (seconds) 654.67 18.95 Relative mass-balance error 2.0e-6 2.8e-8 PARDISO Parallel Direct Solver Simulation time (seconds) 1104.62 21.73 Relative mass-balance error 1.6e-13 4.2e-14
- 29. Summary 息 DHI Unstructured tetrahedral meshing can be combined with layered meshes or used for the entire domain Substantial reduction in mesh size for the same level of geologic detail Direct solvers become applicable to new class of problems
- 30. Thank you and perhaps see you at FEFLOW 2015, September 2125 in Berlin, Germany! 息 DHI