The finite layer method for groundwater flow models

The finite layer method (FLM) is an extension of the finite strip method familiar in structural engineering. The idea behind the method is to discretize two space dimensions using truncated Fourier series, approximating variations in the third via finite elements. The eigenfunctions used in the Fourier expansions are orthogonal, and, consequently, the Galerkin integrations decouple the weighted residual equations associated with different Fourier modes. The method therefore reduces three‐dimensional problems to sets of independent matrix equations that one can solve either sequentially on a microcomputer or concurrently on a parallel processor. The latter capability makes the method suitable for such computationally intensive applications as optimization and inverse problems. Four groundwater flow applications are presented to demonstrate the effectiveness of FLM as a forward solver.