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Analysis of both saturated (groundwater) and unsaturated aquifers is possible. For unsaturated conditions the nonlinear Richards equation is available as well as the van Genuchten-Mualem, Brooks-Corey and Haverkamp equations. Alternatively, for three dimensional regional unconfined aquifers a multiple free surface approach using moving meshes has been developed.
Transient or steady-flow conditions:
The flow and transport can be either transient or steady-state.
Modeling of the Unsaturated Zone
Mass Transport Modeling
Multi or single component transport (species)
The conservation equation is solved for a single component governed by advection, diffusion, mechanical dispersion, retardation, zero and first-order reaction terms.
FEFLOW allows simulating multi-species transport with an arbitrary number of components. Besides an intuitive definition of arbitrary reaction terms in the new equation editor, Degradation, Arrhenius and Monod reactions are available as pre-defined equations.
Altogether, a reactive term can use an arbitrary number of components. The mass transport parameters, like diffusion, dispersion, sorption and reaction rate can be individually edited and spatially distributed.
IFM
Under some circumstances it can be necessary to have more influence on the simulation, data regionalization, visualization, and more. In this case FEFLOW provides a tool called Interface Manager (IFM). The IFM manages an arbitrary number of external modules. An installed, registered, and activated module can access FEFLOW's internal data store and method pool via a published programming interface (API).
Depending on the principle of integration with FEFLOW's internal methods two basic types of interfaces can be subdivided: (1) the external module replaces the FEFLOW-internal methods or (2) the external module extends the internal functionality.
Functions for the open programming interface IFM:
- 'Set' and 'Get' functions for fracture properties
- 'Set' and 'Get' functions for drying curve properties (hysteresis)
- Setting of predictor values for predictor/corrector time-stepping schemes
- Extended functions for boundary constraint conditions
- 'Get' and 'Set' functions for adaptive mesh refinement (AMR) estimators
- Various functions for time-step control parameters, solver types and specific options settings
PEST
The interface to the automatic parameter estimation program allows optimizing transient processes.
MESH GENERATION
Superelement meshThe mesh editor allows to automatically close the actual superelement if you construct more than one, eliminating the laborious task of clicking on existing superelement nodes is no longer necessary.
Gridbuilder
For the generation of the finite element mesh, the mesh generator Gridbuilder is available. Gridbuilder has its main advantages in very flexible refinement along add-ins and polygon borders and in the handling of complex superelement meshes.
Additional options for Triangle mesh generator
Using the Triangle mesh generator, the mesh can be refined along specific sections of polygon borders or add-ins. A target element size can be specified to define the maximum edge length for elements at borders or add-ins.
Edge flipping for mesh improvement
The mesh geometry editor can flip edges for two neighboring elements in triangle meshes. This is useful for improving the mesh quality, and avoiding obtuse angles at specific locations.
Dirichlet, Neumann and Cauchy-type boundary conditions can be specified for flow and mass. A so-called 4th kind boundary condition exists for singular wells. These boundary conditions can be arbitrarily placed at nodal points of a two or three dimensional mesh. All boundary conditions can be specified either as steady-state or as transient conditions.
For each boundary condition constraint formulations can be combined. They represent limitations of boundary conditions and result from the requirement that boundary conditions should only be valid as long as minimum and maximum bounds are satisfied. The constraints can also be time-dependent
Specified Internal Conditions
There are no spatial and temporal limitations in prescribing boundary conditions and their corresponding constraints of a mesh. The boundary conditions are node-related while material parameters are element-related. Both nodal and elemental quantities can be transient if desired.
Stresses
Rainfall or evaporation are normally modeled by sink/source formulations. They may also be time-dependent. Pumping or injection conditions of singular wells are described by a boundary condition of 4th kind. Multi-layer pumping or injection wells are also accommodated in three dimensions.
Optional BC input: Pressure, Seepage Face, Saltwater Head,
Saturation and Moisture Content
Instead of using values of hydraulic head, the Dirichlet boundary conditions can be done by using pressure values, setting a seepage face condition, automatically converting a saltwater head into a freshwater head or setting saturation or moisture content under unsaturated conditions.
Multi-Layer Well Input Dialog
Wells with screens in multiple layers can be input by specifying the top and bottom of the well screen(s), avoiding a manual selection of each slice in the range of the screening.
Layer-Related Evaluation of Fluid Flux For Multi-Layer Wells
For multi-layer wells, the flows into the well in the respective layers can be calculated by using the fluid flux analyzer.
Natural Constraints
FEFLOW allows setting natural constraints on the top and bottom slice to obviate a falling dry of the model or an increasing of the water table above the surface. Users can now set an additional constraint condition to the boundary condition either “water table” or “seepage face” types for the natural constraint.
User-defined reactions and source/sink terms in discrete elements
Arbitrary relationships for multi-species reactions and source/sink terms can be specified in discrete elements using the formula editor.
Automatic switch-off of fracture elements in unsaturated soil
Discrete feature elements are automatically switched off if at one node of the element the pressure is below zero. This is done in both the unsaturated mode using Richards' equation and in phreatic mode.
Mesh inspector for copying discrete feature data
Properties of an existing discrete element can be copied into the input boxes for new elements by hitting the left mouse button while using the Mesh inspector.
Extended Oberbeck-Boussinesq approximation for fracture elements
The extended Oberbeck-Boussinesq approximation is now also applied to discrete feature elements.
PARAMETERS
All parameters are handled on an elemental level, they can differ from element to element and it is possible to consider those as steady-state or transient quantities. Accordingly, parameter heterogenity, zoning or constant settings are arbitrarily possible. The input and assignment of the parameter is done via a graphical problem attribute editor. This attribution encompasses different graphical assignment methods and also interpolation techniques.
A more general programming interface is also available, which allows manipulation of parameters during simulation runs.
Material and Physical Properties
User-defined equations for source/sink and recharge
For the source/sink and in/outflow on top/bottom parameters in flow materials and for the source/sink parameters in mass transport modeling an equation editor is available, so that user-defined relationships are possible.
Reactions in single-species transport can be limited to the fluid or solid phase only
For single-species transport, reactions can be limited to either the fluid or the liquid phase.
Additional parameters for user-defined reaction
The reaction kinetics editor provides additional parameters such as time, time-varying functions, and elemental reference distributions, for application in the user-defined chemical reactions.
Automatic generation of Euler angles for full 3D anisotropy
Using full 3D anisotropy with user-defined Euler angles, the initial Euler angles can be calculated automatically from the layer inclination.
Species-dependent density relationships
For each species a seperate ratio can be specified, considering different concentration-density relationships for the simulated species.
User-defined viscosity relationship
The built-in viscosity relationship can be replaced by user-defined relationships. The formula editor is used to specify an arbitrary equation.
Storage change is considered for time-varying storativity
In case of time-varying storativity, the change in storage due to changed storativity is now considered altered.
Anisotropy
Additional to the axis-parallel and layer-oriented systems of anisotropy, the Eulerian angles can freely be edited for representing complete 3D anisotropy.
Scatter plots for comparison of results and observation data
Scatter point plots are available for comparing both steady-state results with observation values and measured and calculated time curves. The locations of the compared points are indicated on the model domain. Values are shown by tool tips.
Elemental reference distributions
Elemental reference distributions can be defined in the same way as the nodal parameter fields. These user-defined elemental parameter distributions can be used to incorporate arbitrary spatial parameter distributions in user-defined equations.
Import of observation points on multiple slices from shape files
In addition to the observation point names, the slice number to put the observation point can be imported from ESRI shape files.
SOLVERS
The solution of sparse equation systems can be solved either by iterative or direct techniques. As default, and especially for large systems, the following methods are available: Preconditioned Conjugate Gradient (PCG)
Standard preconditioners such as the incomplete factorization (IF) technique and, alternatively, a modified incomplete factorization (MIF) technique based on the Gustafsson algorithm are used.
Alternatives for the CG-like solution of the unsymmetric transport equations include:
- Restarted ORTHOMIN (orthogonalization-minimization) method
- Restarted GMRES (generalized minimal residual) technique
- Lanczos-type methods such as CGS (conjugate gradient square), BiCGSTAB (bi-conjugate gradient stable) and BiCGSTABP (postconditioned bi-conjugate gradient stable)
Crout Decomposition Scheme
For small or ill-posed problems, direct Gaussian elimation techniques for symmetric and unsymmetric matrices are available. Here, the Reverse Cuthill-McKee (RCM) nodal reordering technique are used to minimize fill-in entries of the matrices.
New version of SAMG, supporting parallel computing
The OpenMP version of SAMG 2.2 supports parallel computing on machines with multiple processors and/or multiple-core processors. So now even the solution process itself can be done in parallel.
SAMG
The solver SAMG, especially approved for steady state problems, can be efficiently used for transient and mass transport models. The reduction of simulation time can be formidable with SAMG’s parallel processing capabilities.
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 are provided to minimize numerical dispersion
- Picard and Newton iterative techniques for non-linear flow problems and adaptive time stepping
- Contaminant transport processes include advection, hydrodynamic dispersion, linear and non-linear 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 & POST PROCESSING
Feflow supports a wide class of subsurface flow, mass transport problems and provides an open data interface for importing, exporting (GIS interface) and programming (interface manager IFM) and also excompasses many graphical tools in the post processing analysis of the results. Transient particle tracking
For an exact chase of particle tracks the new transient particle tracking can be used. The tracks can be computed for the simulated time range or a specific time period. Furthermore the particle start points or lines can be loaded and exported. In contrast to previous FEFLOW versions, the particle starting points around wells can be either distributed equally, spaced or corresponding to the flux distribution.
Display and Analysis
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
- 3D projections
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3D Cut-Aways
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 files
Fence Diagrams
FEFLOW creates cross sections and true fence diagrams to display mass concentrations, computed hydraulic heads, streamline velocities, moisture & saturation distributions, and pressure distributions.
Three-Dimensional Projections
Three-dimensional projections are helpful when describing mass concentrations, computed hydraulic heads, streamline velocities, moisture & saturation distributions, and pressure distributions. The three-dimensional projections options display these data overlaying the geo-referenced map objects for a better understanding of the simulation.
Three-Dimensional Cut-Aways
You can define the cut-away by inserting screen related position coordinates in the menu or by moving the three-dimensional handlers on the models body via the mouse. The Cut-Away-Viewer gives the user the ability to define a block portion of the model's body to be cut-away. It is a helpful tool to view parameter distributions in the inner part of the model.
Budget Analyzer
The 'Budget' analyzer computes quantities of fluid masses and contaminant masses entering or exiting the simulated region, sub-regions 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:
WGEO map tool replaces FEMAP on Windows
On Windows systems, the georeferencing tool FEMAP, is replaced by the software WGEO for georeferencing, geoimaging and coordinate conversion. A license for WGEO Basis is delivered with FEFLOW.
FEFLOW Explorer
FEFLOW Explorer allows three dimensional visualizing of model properties and simulation results. Some of the features are automatic rotation, fly-over and video export. Alternatively hardware-accelerated or software-optimized OpenGL graphics can be used.
New bullet vector plot style
This style uses equal-sized line segments that are individually oriented and colored according to the local flow-vector orientation and magnitude, respectively. The vector direction of each line segment is illustrated by opacity, increasing from fully translucent to fully opaque along the segment. Compared to the arrow plot style, more detail of the flow field can be discerned especially in the slower-moving regions.
Wells and observation points can be shown
Wells and observation points can be displayed as emphasized “points”. In addition, wells can also be displayed via surface flags and as pipes.
More supported image/map formats including 2D ESRI-shape files
In addition to the standard pixel image formats, vector images including 2D ESRI-shape files can be displayed as surface-mapped overlays. Multiple maps can be shown simultaneously.
Individual layers and slices accessible as plotting domains
Individual layers, slices, and the vertical hull can be used as plotting domains.
Editable color sequences
The color sequence associated with a data source can be individually edited via a convenient dialog. Color sequences are also easily inverted, exported, and imported. Several predefined sequences are available.
Animated clipping and dynamic plot-feature visibility with automatic cross-fading
Besides simulation time and object positioning, the autopilot now also controls clipping planes and plot-feature visibility over the duration of the presentation. The new dynamic clipping allows presentation (movie) effects such as a gradually extending cut-out section progressively exposing internal isosurfaces. Dynamic plot-feature visibility can be used to display multiple data sources in sequence, or to display features such as the finite-element mesh or a surface map during only a portion of the entire presentation, with smooth cross-fading at the beginning and end of the visibility period.
Off-screen (background) export rendering
During image (.bmp) or movie (.avi) export, graphics are rendered directly to the file without any screen capturing. This makes it possible to minimize the FEFLOW-Explorer window and to keep working while exporting a movie.
Redesigned memory layout permits loading of larger problems
All visible geometry vertices and their attributes are now managed in a way that permits direct, fast drawing without having to use memory-expensive ‘display lists’ as in version 1.
FELOW includes a user's manual, two reference manuals, one dongle, and an installation CD-ROM. Technical support and upgrades are available for a duration of 30 days free of charge. An annual maintenance fee will be charged beyond the free 30 day period. Contact SWS for more information regarding the annual maintenance fee.
HARDWARE REQUIREMENTS
Hardware Requirements (PC)
Hardware Requirements (UNIX)
64-bit technology for Windows and Linux
FEFLOW is now available for the 64-bit versions of Windows (XP X64 Edition, Server 2003 X64 Edition, and Vista X64 Edition) and Linux (SUSE 9.2, 9.3, 10.0, 10.1, Fedora Core 4 and 5, Ubuntu 6.06). 64-bit technology is essential for running large models requiring more than about 2 GB of RAM.
Parallel computing on Windows and Linux
Parallel computing on multi-processor machines or computers with multi-core processors is now supported on both Windows and Linux systems.
Hummingbird Exceed as default X server
The X server XVision is replaced by Hummingbird Exceed as the default X server on Windows systems.
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