3DSALT : a three-dimensional finite element model of density-dependent flow and transport through saturated-unsaturated media
Yeh, Gour-Tsyh (George), 1940-; Chang, Jing-Ru.; Gwo, Jin-Ping.; Lin, Hsin-Chi J.; Richards, David R.; Martin, William D.
Instruction ReportAbstract: This report presents the user's manual of 3DSALT, A Three-Dimensional Finite Element Model of Density-Dependent Flow and Transport Through Saturated-Unsaturated Media. The model is designed for generic application. The model is developed specifically for solving seawater intrusion problems in subsurface media. It consists of a flow module and a transport module. In comparison to conventional finite element (including both Galerkin and upstream finite elements) or finite difference (including both central and upwind finite differences) models, the transport module of 3DSALT offers several advantages: (A.) it completely eliminates numerical oscillation due to advection terms, (B.) it can be applied to mesh Peclet numbers ranging from 0 to infinity (conventional finite element or finite difference models typically impose unduly severe restriction on the mesh Peclet number), (C.) it can use very large time-step sizes to greatly reduce numerical dispersion (in fact, the larger the time-step, the better the solution with respect to advection transport; the time-step size is limited only by the accuracy requirement with respect to diffusion/dispersion transport, which is normally not a very severe restriction), and (D.) the hybrid Lagrangian-Eulerian finite element approach is always superior to and will never be worse than its corresponding upstream finite element method. Because of these advantages, 3DSALT is ideal for simulating density-dependent flow and advection-dominant transport. For each site-specific application, 58 control integers must be assigned using the parameter statement in the MAIN program. In addition, if the material properties are specified by analytical functions, the subroutine SPROP must be modified by the users. Sources/sinks and boundary values as functions of time can also be specified by analytical functions. Under such circumstances, the users should provide such functions in subroutines ESSFCT, WSSFCT, DBVFCT, VBVFCT, CBVFCT, and NBVFCT. Input to the program includes the control indices, properties of the media either in tabular or analytical form, the geometry in the form of elements and nodes, and boundary and initial conditions either in tabular or analytical form. Principal output includes the spatial distribution of pressure head, total head, moisture content, Darcy velocity components, concentration, and material fluxes at any desired time-step. Fluxes through various types of boundaries are output. In addition, diagnostic variables, such as the number of nonconvergent nodes and residuals, may be printed if desired for debugging purposes. Appendix A presents a data input guide for site-specific application. Appendix B provides the physical bases and mathematical foundation for describing density-dependent flow and material transport. Appendix C gives the numerical detail in approximating the governing equations.
Hydraulics Laboratory (U.S.)Engineer Research and Development Center (U.S.)
Density-dependent flow; Lagrangian-Eulerian approach; Finite element method; Saturated-unsaturated flow; Groundwater; Groundwater flow; 3DSALT; Computer program
Instruction report (U.S. Army Engineer Waterways Experiment Station) ; HL-94-1.
Approved for public release; distribution is unlimited.