Adaptive Mesh Refinement of 3D saturated-unsaturated hydrological and transport models

Unsaturated water flows at watershed scale or Darcy-scale are generally described by the Richardson-Richards equation. This equation is highly non-linear and simulation domains are limited by computational costs. The porousMultiphaseFoam toolbox, is a Finite Volume tool capable of modeling multi-phase flows in porous media, including the solving of the Richardson-Richards equation combined with the transport equation. As it has been developed using the OpenFOAM environment, the software is natively fully parallelized and can be used on super computers. Despite all its perks, the toolbox still suffer from expensive computational cost in 3D, highlighted by a calibration method developed last year to validate the 3D model against the historic 2D and 1D+2D models. In an attempt to reduce those, Adaptive Mesh Refinement (AMR) method has been included into the toolbox. The main issue faced by the method is the highly anisotropic mesh, with cells having horizontal characteristic lengths up to 100 times bigger than the vertical one. We present here the results obtained using the AMR, and tools to evaluate its efficiency on anisotropic meshes. Particularly, we take interest in the total CPU time, the mesh size and the number of linear iteration required to solve the problem. We show results using both 3D hydrological and transport solvers.