Civil and Water Engineering

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A time-dependent Green’s function-based model for stream-unconfined aquifer flows
(Water research commision, 2004-07-01) Taigbenu, A.E.
A numerical formulation that is based on the Green element method (GEM), which incorporates a time-dependent Green’s function, is used to solve transient two-dimensional flows of stream-unconfined aquifer interaction. The Green’s function comes from the fundamental solution to the linear diffusion differential operator in two spatial dimensions. In classical boundary element applications, this Green’s function has found use primarily in linear heat transfer and flow problems; its use here for the nonlinear stream-unconfined aquifer flow problem represents the computational flexibility that is achieved with a Green element sense of implementing the singular integral theory. The nonlinear discretised element equations obtained from numerical calculations are linearised by the Picard and Newton-Raphson methods, while the global coefficient matrix, which is banded and sparse, is readily amenable to matrix solution routines. Using four numerical examples, the accuracy of the current formulation is assessed as against an earlier one that incorporates the Logarithmic fundamental solution. It is observed that comparable accuracy is achieved between both formulations, indicating that the current formulation is a viable numerical solution strategy for the stream-aquifer flow problem.