A parallel finite element code fon nonlinear leaky aquifer systems.

Developing parallel codes for computing the nonlinear flow in multiaquifer porous systems is an important task both for improving model efficiency and for performing large real-life simulations. Multiaquifer systems consist of sandy and clayey alternating layers. In this paper, highly compressible multiaquifer systems are considered, where some hydraulic parameters depend on the potential head, thus the flow inside some layers is governed by nonlinear equations. An effective procedure for solving these equations is developed, relying upon The partition of the solution procedure into layer-wise steps. By assigning to each processor the computation of the flow inside a suitable set of layers, the iterative solution procedure can be efficiently implemented on a parallel super-computer. Using such a domain decomposition strategy, a satisfactory degree of parallelization is achieved when computing the flow in a realistic nonlinear multiaquifer system, employing a CRAY T3D massively parallel computer. Performing test simulations on real-life multiaquifer systems, the recorded speed-ups are as large as 1.89, 3.34. 5.37, with 2, 4, 8 processors, respectively. The importance of load balance and information exchange in casting the parallel performances of the code is also analyzed