Research Day – Jan 25

This week we will have a Research Day talk by


Time: Wednesday January 25, 2023, 10:15am
Room 00.133 (Animationslabor) at LSS 10, Cauerstraße 11.

If there are requests, we will organize a hybrid meeting also via zoom. (contact:

Scalable Block Preconditioners for Coupled Thermo-Hydro-Mechanics Problems

Nicolas Tardieu

We are interested in the modelling of coupled thermo-hydro-mechanical (THM) problems that describe the behaviour of a soil in which a weakly compressible fluid evolves. The soil is modelled as a porous medium and the fluid is subjected to various mechanical, thermal and hydraulic loadings [1]. This model is used for the evaluation of the THM impact of high-level activity radioactive waste exothermicity within a deep geological disposal facility build in a clay-based host rock. The parallel and scalable solution of the linearized equation system is the objective of this work.

Academic work has been carried out on models involving solid mechanics and hydraulics [2] [3] or involving THM but with little interest on linear solvers [4]. In this talk, we shall present the definition of a block preconditioner for the fully coupled THM equations. A block Gauss-Seidel preconditioner is set up, in which a multigrid method is used to precondition each block. The method is implemented in code_aster, the massively parallel open source general purpose finite element solver developed at EDF R&D [5].

Numerical results for linear THM tests reflect the good performance of the proposed preconditioner that shows to be weakly scalable until more than 2000 cores and more than 1 billion degrees of freedom. Furthermore, the iteration count of the iterative solver is independent of the mesh size and robust parameter-wise.


[1]   Poromechanics, Coussy, O., John Wiley & Sons, 2004.
[2]   Efficient block preconditioners for the coupled equations of pressure and deformation in highly discontinuous media, Haga, J. B., Osnes, H. and Langtangen, H. P., Int. J. Numer. Anal. Meth. Geomech., 35: 1466-1482, 2011.
[3]   Block-partitioned solvers for coupled poromechanics: A unified framework, J. A. White, N. Castelletto, H. A. Tchelepi, Computer Methods in Applied Mechanics and Engineering, Volume 303, Pages 55-74, 2016.
[4]   Flexible parallel implicit modelling of coupled thermal–hydraulic–mechanical processes in fractured rocks, M. Cacace, A. B. Jacquey, Solid Earth, 8, 921–941, 2017