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Detailed Description



Introduction to Feflow

Over the last two decades the environmental industry has seen a dramatic increase in the application, understanding and acceptance of groundwater numerical modeling techniques for simulating groundwater flow and contaminant transport. During this time, the USGS' MODFLOW and MODPATH, and the popular contaminant transport program MT3D, have become worldwide standards for 3-D groundwater flow and contaminant transport modeling. Unfortunately, when you are faced with more challenging problems involving complicated geology, unsaturated flow, density-dependent flow (salt water intrusion), or thermal convection, these traditional modeling programs have proven to be unsuitable.

Feflow is the first complete groundwater modeling software package to successfully combine powerful graphical features with sophisticated analysis tools and robust numerical algorithms for:

  • Density-dependent flow (salt water intrusion)
  • Transient or steady-state flow
  • Saturated and unsaturated flow
  • Multiple free surfaces (perched water table)
  • Mass and heat transport

Feflow has been specifically designed to meet the advanced technology requirements of expert modeling professionals involved in complex groundwater modeling projects. The primary components of Feflow include:

  • A comprehensive selection of graphical tools for building the finite element mesh, assigning property zones and setting boundary conditions
  • Data import and interpolation routines including an ArcInfo (ESRI) GIS data interface
  • Robust numerical algorithms and solution techniques
  • Real-time data interpretation
  • State-of-the-art 3-D visualization

These components ensure an efficient process for building the finite element model, running the simulation, and visualizing the results. Feflow is a fully-integrated modeling environment with a full-featured graphical interface and powerful numeric engines that allow the user to:

  1. Graphically create finite element meshes for simple or complex geological formations
  2. Import and link data from external sources via Feflow's GIS/DATA Coupling exchange system
  3. Assign all necessary flow and transport parameters
  4. Run complex model simulations
  5. Visualize the simulation results in two- or three-dimensions

Try Feflow today and see why it is the expert's choice for advanced groundwater
 modeling applications.

Professional Applications of Feflow

  • Groundwater Modeling - Determine the spatial and temporal distribution of groundwater heads and contaminants
  • Contaminant Transport - Estimate the duration and travel times of a pollutant in aquifers
  • Seawater Intrusion - Evaluate the impact of sea water intrusion due to groundwater pumping and/or mining activities along coastal regions
  • Nuclear Waste Disposal - Simulate the combined effects of geothermal gradients and saline groundwater flow for deep well injection of nuclear wastes
  • Mine Dewatering - Design and optimize pumping well locations and pumping rates and determine the influence of dewatering activities on local and regional groundwater supplies
  • Groundwater Remediation - Evaluate remediation alternatives, plan remediation strategies, and optimize groundwater remediation system designs
  • Dam Seepage - Analyze moisture dynamics and seepage through the dam
  • Aquifer Recharge - Predict rates of infiltration/aquifer recharge due to precipitation, storm water retention ponds or artificial aquifer recharge schemes

Main Features of Feflow

  • Advanced 3-D graphically-based groundwater modeling environment
  • Saturated and unsaturated flow and contaminant transport (2-D and 3-D)
  • Convective, conductive, and thermo-dispersive heat transport
  • Fully-transient, semi-transient and steady-state flow and transport processes
  • Confined and unconfined aquifers, multiple free surfaces for perched water tables
  • Cellular convection processes used for gravity driven, thermally driven, and double diffusive convection ideally used for saltwater intrusion
  • Powerful finite element mesh generation capabilities
  • Database and GIS-Coupling for efficient handling of environmental data
  • Integrated data regionalization routines for interpolating discrete data points
  • Graphically assign boundary fluxes and transfer conditions
  • Visualize simulation results using high impact, 3-D visualization capabilities including fence diagrams, pathlines, isosurfaces, arbitrary cutaways, isochrones, model rotation, and flow vectors
  • Create detailed budget reports for fluid flow, species concentrations and heat flow
  • New Interface Manager for linking Feflow to third party software or custom generated subroutines

Model Design Features - Starting a Project

The hierarchical structure of the Feflow interface facilitates a very quick learning curve that allows the user to create complex models in a short amount of time. The following section provides a general description of the steps involved in creating a 3-D finite element model using Feflow. Click on graphics to view a larger enhanced version (a few are not larger).

Defining a Problem in Feflow

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 modelFeflow  graphic 3 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

Problem Class:

  • Flow Only
  • Steady Flow
  • Transient Flow

 Flow and Mass/Heat Transport

  • Steady flow, steady transport
  • Steady flow, transient transport
  • Transient flow, transient transport

Feflow  graphic 4Generating a Finite Element Mesh in Feflow

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.

Feflow  graphic 5Refining 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.

Mesh refinement can be conducted on a single element, a group of selected elements, or on a global basis. Alternatively, mesh refinements can be predetermined by importing ESRI Shape files.

Element types available in the 2-D Feflow module include the linear 4-nodal and 8-nodal quadrilateral elements and the linear 3-nodal and 6-nodal triangular elements. Element types available in the 3-D Feflow module include 8-nodal and 20-nodal quadrilateral prisms and the 6-nodal and 15-nodal triangular prisms.

Feflow  graphic 6Create 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 and the geometric relationships 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 ( top or bottom of stratigraphy).

Feflow  graphic 7Import 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), and ESRI Shape File (*.shp).

Feflow  graphic 8Feflow 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 in Feflow

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

Feflow  graphic 9

Imported model properties can be regionalized to a local model region or extrapolated to the entire model domain.

Feflow model properties are divided into three major categories that define the various characteristics and conditions of both the flow and the transport model.

Flow Attributes

  • Flow Initials - initial hydraulic head, saturation, moisture content or pressure
  • Flow Materials - conductivity (Kx, Ky, Kz), storativity, storage compressibility, and density ratio
  • Flow Boundaries - head (first type), flux (second type), transfer (third type), well (fourth type)

Transport Attributes

  • Transport Initials - initial mass concentration (or temperature), density and viscosity effects
  • Transport Materials - porosity, sorption, molecular diffusion, longitudinal dispersivity, transverse dispersivity, decay rates, source/sinks and transfer rates
  • Transport Boundaries - mass (1st type, Dirichlet), flux (2nd type, Neumann), transfer (3rd type, Cauchy), well (4th type)

Feflow  graphic 10 Feflow  graphic 11

Feflow  graphic 12Parameter Association
This 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 pipe lines from the Feflow parameter list to a database is just a matter of clicking the links. 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.

Running the Feflow Model Simulation

Feflow  graphic 13 Feflow  graphic 14

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.
  • Real-time graphs of transient heads and concentrations at a number of points throughout the model domain are plotted during the solution process.
  • Simulation progress can be paused at any time to view intermediate results in three dimensions.

Visualization of Results in Feflow

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.

Feflow  graphic 15 Feflow  graphic 16

Feflow  graphic 17Fence 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.


Feflow  graphic 183-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.

Feflow  graphic 19
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.

Feflow  graphic 20Budget 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:

  • Fluxes along outer or inner boundaries, i.e., borders occupied with Dirichlet, Neumann or Cauchy boundary conditions (1st, 2nd and 3rd kind)
  • Injections and withdrawals through single wells (4th kind)
  • Areal fluxes due to infiltration, recharge, leakage etc.
  • Imbalance: Gain (+)/Loss(-)


Feflow  graphic 21FEPLOT
FEPLOT has been developed as a design and plotting tool for Feflow generated vector data. FEPLOT 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.


Feflow Documentation

Feflow includes a User's manual, (2) Reference Manuals, one Dongle, and an installation CD-ROM. Technical support and upgrades are available for a duration of 6 months free of charge. An annual maintenance fee will be charged beyond the free six-month period (optional but recommended). Contact us for more information regarding the annual maintenance fee.

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