Density-Dependent Flow

Contaminant Transport

Thermal Transport

Advanced Numerical Methods

GIS Data Interface

3-D Visualization

 FEFLOW was developed by WASY.

Defining a Problem

The specifications of all model attributes on a given finite element mesh are completed in the FEFLOW Problem Classifier Menu. It allows you to define model physics, specify problem classes, control data and time characteristics, and manipulate mesh data. The following model classifications are available:

Model Type:

• Saturated Media
• Unsaturated/Variable Saturated Media

• Flow Only
• Steady Flow
• Transient Flow
   
• Flow and Mass/Heat Transport
• Steady flow, steady transport
• Steady flow, transient transport
• Transient flow, transient transport

Generating a Finite Element Mesh

The most common procedure to defining a FEFLOW model area is through the use of overlain maps. FEFLOW can import various map files to act as templates for generating the super-element mesh. Once the outer boundary of the mesh is defined, FEFLOW automatically generates a finite element mesh based on a user-defined number of elements.

Refining a Finite Element Mesh
Once the super-element mesh has been generated, mesh refinement is conducted through the MESH Editor. Unlike finite difference models such as MODFLOW, FEFLOW's finite element approach allows the user to perform local mesh refinements only in the areas of interest and avoids creating excessive elements.

Create Multiple Layers/Slices
The 3-D Layer Configurator allows the user to add or delete slices at any given Z-elevation in the model. In addition, the user can define the extent of the layers throughout the model domain and the geometric relationships shared between layers. Z-elevations can also be manually assigned to every slice or imported from a database for greater representation of the variable layer thicknesses (e.g., top or bottom of stratigraphy).

Import Variable Surfaces
FEFLOW can import and interpolate raw data to create variable surfaces for accurate representation of variable layer thicknesses found in the field. Data formats include:

• ASCII Triplets (XYF) (*.trp),
• ASCII Database (XYF) (*.dat),
• dBASE IV (XYF) (*.dbf),
• ESRI Shape File (*.shp).

FEFLOW also allows the user to choose which interpolation technique best suits their data set. The popular Kriging technique, Akima, Inverse Distance Weighting or 1-D interpolation (only for boundary conditions), can be used for calculating the variable surfaces. Once completed, the model layers including the variable surfaces can be seen in three dimensions.

Assigning Model Properties

FEFLOW has a comprehensive selection of graphical tools for assigning and modifying all model properties (e.g., flow, mass transport and heat transport properties). The graphical tools allow you to assign properties using:

• A global-uniform value for the entire model
• Element-specific values for selected elements
• Node-specific values for selected nodes
• Uniform values to an area defined by a box
• Stored values from an external database (x, y, value) or ARC/INFO GIS file

• Transport Initials - initial mass concentration (or temperature), density and viscosity effects

Parameter Association
The Parameter Association menu links spatial data in the form of polygons or lines (ASCII or Shape files) with attribute data from databases (ASCII, Shape file or dBASE). Defining the pipelines from the FEFLOW parameter list to a database is just a matter of clicking the links. The model properties can be imported and regionalized to the entire model region, local zones within the model, or along a digitized line of nodes or elements.

Advanced Numerical Methods
FEFLOW uses a Galerkin finite element numerical approach with a selection of numerical solvers and state-of-the-art tools for controlling and optimizing the solution process including:

• Fast and direct solvers such as the PCG and Restarted ORTHOMIN Methods with preconditioning.
• Variable types of solution up-winding techniques to minimize numerical dispersion.
• Picard and Newton iterative techniques for nonlinear flow problems and adaptive time-stepping.
• Contaminant transport processes include advection, hydrodynamic dispersion, linear and nonlinear sorption isotherms, and first order chemical non-equilibrium.
• Automated adaptive mesh refinement scheme to optimize the numerical solution in regions where steep gradients exist.

FEFLOW comes with state-of-the-art visualization capabilities for creating high impact, three-dimensional graphics for displaying model results:

• Isolines and fringes;
• Velocity vector fields;
• Particle tracking (forward/reverse);
• Cross sections and fence diagrams;
• 3-D projections; and
• 3-D Cutaways.

All graphical editing is completed through FEPLOT, the Microsoft Windows-based graphical design tool included with FEFLOW. Captured plots can be georeferenced to ensure exact overlay of the map objects. File formats include FEPLOT *.plx files, ESRI shape files or ARC/INFO compatible ASCII (Generated) files.

Fence Diagrams
FEFLOW creates cross sections and true fence diagrams to display mass concentrations, temperature distributions, computed hydraulic heads, streamline velocities, moisture and saturation distributions, and pressure distributions. Line segments can be arbitrarily selected using the graphical interface and can be exported for presentation purposes.

3-D Projections
3-D Projections are helpful when describing mass concentrations, temperature distributions, computed hydraulic heads, streamline velocities, moisture and saturation distributions, and pressure distributions. The 3-D projections options displays these data overlaying the georeferenced map objects for a better understanding of the simulation.

3-D Cutaways
The Cutaway-Viewer gives the user the ability to define a block portion of the model's body to be cutaway. It is a helpful tool to view parameter distributions in the inner part of the model. You can define the cutaway by inserting screen related position coordinates in the menu or by moving the 3-D handlers on the model's body via the mouse.

Budget Analyzer
The 'Budget' analyzer computes quantities of fluid masses and contaminant masses entering or exiting the simulated region, subregions or boundary sections. The balance computation takes into account only mesh nodes occupied by values for areal recharge or boundary conditions as listed below. The computed quantities for the fluid and contaminant mass are:

FEPLOT
FEPLOT has been developed as a design and plotting tool for FEFLOW generated vector data. FEPLOT is a full 32-Bit Windows application that allows the user to easily georeference plots as overlays, add text for reports, and print the simulation graphics. Plots can also be saved as templates for future use when preparing reports. Acceptable georeferenced file formats include: *.plx files, ESRI Shape files and ARC/INFO compatible ASCII files.