Solution of the Equations

• We use preconditioned conjugate-gradient method to solve our equations on an unstructured hexahedral mesh.

• The operator used for preconditioning is a 7-point pure cell-centered discretization that results from our full scheme when the off-diagonal components of the matrices are set to zero. This is completely analogous to the preconditioner used in [2].

• The conjugate-gradient method is also be used to solve the preconditioning equations.