FEMWATER: A Finite Element Model of WATER Flow Through Saturated-Unsaturated Porous Media: First Revision

摘要

FEMWATER is designed to treat heterogeneous and anisotropic media consisting as many geologic formation as desired; to consider spatially and temporally distributed as well as point sources/sinks; to accept the prescribed initial conditions or to obtain them by simulating steady state version of the system under consideration; to deal with transient head distributed over the Dirichlet boundary; to handle time dependent fluxes due to pressure gradient varying along the Neumann boundary; to treat time-dependent total fluxes distributed over the Cauchy boundary; to automatically determine variable boundary conditions of evaporation, infiltration, or seepage on the soil-air interface; to include the off-diagonal hydraulic conductivity components in the modified Richards' equations for dealing with cases when the coordinate system does not coincide with the principal directions of the hydraulic conductivity tensor; to provide two options of treating the mass matrix - consistent and lumping; to provide three alternatives of approximating the time derivative term-Crank-Nicolson central difference, backward difference, and mid-difference; to give three options for estimating the nonlinear matrix; to include two options for solving the linearized matrix equations; to include both quadrilateral and triangular elements to facilitate the discretization of the region; to automatically reset time step size when boundary conditions or source/sinks change abruptly; to check the mass balance computation over the entire region for every time step; and to consider cases of axis-symmetrical problems. 30 refs., 17 figs., 3 tabs. (ERA citation 12:049420)