Symmetric and unsymmetric block preconditioning for the iterative solutionto FE coupled consolidation

The repeated solution in time of the linear system arising from the Finite Element (FE) integration of coupled consolidation equations is often a major computational effort. This system can be written in either a symmetric or unsymmetric form, thus calling for the implementation of different preconditioners and Krylov subspace solvers. The present communication investigates the performance of ad hoc block preconditioners used with either SQMR or Bi-CGSTAB. The symmetric and unsymmetric forms of the FE consolidation equations prove to be almost equivalent as to the convergence rate of SQMR and Bi-CGSTAB, respectively, with block preconditioners usually outperforming traditional ILU-based preconditioners.