A high performance non-linear simulation

by HM Ngo EDF / DPN / UTO and T. De Soza, EDF R&D / AMA

This simulation represents a roll-expanded tube in a hemispherical bottom, subjected to pressure loading. The model is fairly large : 750.000 degrees of freedom with a quadratic mesh. It has two major nonlinearities :

• contact on a small part of the model (less than 250 nodes) in the area of the tube crossing ;
• a Von Mises elasto-plastic behavior (non-linear isotropic hardening).

The computation time is mainly related to the linear systems solving, it is crucial to reduce the cost of this phase.

In version 10, with some care in the setting of the direct solver MUMPS, the calculation requires about 23 GB of memory and does not even converge in more than 12 hours.

In version 11, three recent advances in Code_Aster can be used to advantage :

• the generalized Newton method for contact-friction ;
• the Newton-Krylov method to reduce the nonlinear time resolutions ;
• the iterative solver PETSC associated with the MPI parallel version of Code_Aster.

This calculation was at the limit of feasibility with the version 10. In the end, it runs with the version 11 in 35 minutes on 64 processors with a global required memory less than 15 Go.