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A parallel software for a saltwater intrusion problem

A parallel software for a saltwater intrusion problem. E. Canot IRISA/CNRS J. Erhel IRISA/INRIA Rennes C. de Dieuleveult IRISA/INRIA Rennes. Outline. Introduction Model of saltwater intrusion problem Parallel Implementation Results Conclusion. Introduction.

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A parallel software for a saltwater intrusion problem

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  1. A parallel software for a saltwater intrusion problem E. Canot IRISA/CNRS J. Erhel IRISA/INRIA Rennes C. de Dieuleveult IRISA/INRIA Rennes

  2. Outline • Introduction • Model of saltwater intrusion problem • Parallel Implementation • Results • Conclusion

  3. Introduction Context Effect of pumping in coastal aquifers Necessity to predict the evolution of the water supply.

  4. Introduction Presentation of the software • Simulation of density driven coupled flow and transport in a porous media • Based on TVDV-2D software developped at IMFS in Strasbourg • Originally sequential

  5. Goals • Obtain good performances thanks to parallelism • Allow large scale simulation (Future goal : extend to 3D geometry)

  6. Fluid equations • Generalised Darcy law: • Conservation of mass:

  7. Convection Diffusion Transport equation • Solute mass conservation equation: • State equations

  8. Coupled Model Model FLOW (MFE) TRANSPORT convection (DFE) dispersion (MFE)

  9. Coupled Model Model concentration FLOW velocity TRANSPORT

  10. Coupled Model Strong Coupling Time n Velocity FLOW TRANSPORT Fixed-point scheme Density Concentration Stopping criterion Time n+1

  11. Parallel implementation Model FLOW Parallel linear solvers TRANSPORT

  12. Parallel implementation Parallel sparse solver Use of MUMPS (« MUltifrontal Massively Parallel Solver »), a free package for solving linear systems of equations Ax=b (direct method): • Adapted for sparse unsymmetric, and symmetric definite positive matrices. • Three steps: symbolic factorisation, numerical factorisation and triangular solving.

  13. Parallel implementation Global parallelisation • Partitioning mesh thanks to METIS, a free package for partitioning graphs, meshes and for producing fill reducing orderings for sparse matrices. Partitioning example with 5 parts

  14. Results Test case : Henry Stable test case

  15. Results Choice of the network • Tests on a Fast Eternet network (100Mb/s) with bi-processors Intel Xeon (CPU 2.4Hz, cache 512Kb) Poor results Use of a Myrinet network (2Gb/s)

  16. Results Choice of the MUMPS option Time spent in MUMPS for different methods of pivot order with mesh 254x126 elements for the Henry test case and 10 time steps.

  17. Results Parallel Results Time results with MUMPS and the Henry problem on 2D meshes.

  18. Conclusion Conclusion - Perspectives • 3D geometry • Parallelisation of the visualisation • Improved coupling

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