Solver for Mixed Finite-Element

Mixed finite-element methods have several features that are attractive in the numerical simulation of groundwater flow. Chief among these is the possibil-ity of computing Darcy velocities whose accuracies are comparable to those of the computed hydraulic heads. Much current research centers on solving the large linear systems that arise from mixed finite-element discretiiations. We examine an iterative method that largely overcomes the poor condition-ing associated with fine spatial grids and highly variable aquifer properties. The method incorporates a multigrid scheme inside an outer iteration whose convergence rate is independent of grid mesh size and variations in hydraulic conductivity. As we demonstrate, the multigrid algorithm is amenable to ef-fective parallelization on distributed-memory machines, making the overall algorithm a highly efficient one in such computing environments