On a MIC(0)MIC(0) preconditioning of non-conforming mixed FEM elliptic problems

In this paper we analyze a preconditioner for mixed finite element systems arising in the approximation of a second order elliptic problem with Neumann boundary conditions by triangular non-conforming elements. This problem stems from the so called projection methods for the unsteady Navier–Stokes equations and is one of the most computationally intensive parts of the method. The present study is focused on the efficient implementation of the modified incomplete LU factorization MIC(0)MIC(0) as a preconditioner in the PCG iterative method for the reduced Schur complement system following from the mixed formulation of the pressure Poisson problem. The presented model analysis and the related set of numerical tests illustrate well the potential of the proposed approach.