KWRRI Research Reports


A two-dimensional transient model for flow through saturated-unsaturated porous media is developed, The model numerically solves the pressure head dependent or moisture content dependent form of Richard's equation. The model code uses isoparametric quadratic triangular and/or quadrilateral finite elements for the geometric representation and for the weak Galerkin spacial integrations. An implicit, unconditionally stable single-step numerical time integration scheme with an oscilliatory noise reduction option is utilized for the temporal discretization. The highly efficient symmetric skyline (profile) solution scheme is used to solve the resulting simultaneous equations. The nonlinear subsurface flow parameters are approximated using cubic spline interpolation. The element material properties can be independently defined thus permitting the modelling of layered geologic formations, Derivative smoothing is presented for the post-calculation of Darcian velocities. Currently, the program is limited to time varying specification of pressure head or moisture content and fluxes. Several sample problems are presented illustrating the accuracy and validity of the developed model.

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The research on which this report is based was financed in part by the U.S. Department of the Interior, as authorized by the Water Research and Development Act of 1978. P.L. 95-467