A Robin-Robin preconditioner for an advection-diffusion problem

Abstract The Neumann-Neumann method is used as a preconditioner in domain decomposition methods applied to symmetric problems. We generalize it to the case of nonsymmetric operators. The new preconditioner is based on solving boundary value problems with Robin boundary conditions. Its derivation at the continuous and discrete levels are given. Numerical results are shown for both conforming and nonconforming grids (mortar method).