Investigation on Iterative Linear Solvers Suitable for the Dual Lagrange Multiplier Method

Abstract

In the dual Lagrange method used in a mortar finite element method, a block matrix with respect to the slave DOFs of the constraint matrix becomes a diagonal matrix due to the biorthogonal shape functions. This property makes the elimination of the slave DOFs easily, and the reduced linear system can be solved by the conjugate gradient method. In the present study, this approach is compared with the conjugate projected gradient method and the BDD-MPC method.