Micro-FEM is the original DOS version of MicroFEM for Windows. It is an integrated large-capacity finite-element microcomputer program for multiple-aquifer steady-state and transient groundwater flow modeling

Program characterization
Product information
Program parts
Inner workings
Screenshots

Program characterization
The DOS package of Micro-Fem is a set of several programs which takes you through the whole process of groundwater modeling, from the generation of a mesh through the stages of preprocessing, calculation, postprocessing, graphical interpretation and plotting. 
Confined, semi-confined, phreatic and leaky multiple-aquifer systems can be simulated with a maximum of 16 aquifers. The maximum number of nodes is 12.500 nodes.
No limitations are set to the number of wells. One of the outstanding features of Micro-Fem is the user-friendly interface. Full graphics control makes the otherwise time-consuming and error-prone process of model parameter input easier. The same is true for the interpretation of the results; the visualization of contours, flowlines, flow vectors, etc. is achieved with just a few keystrokes. Results can be saved in the HPGL and DXF format.

Its capacity, flexibility and ease of use have made Micro-Fem the most widely used groundwater modeling package in the Netherlands. Its users comprise government agencies,consultants and universities.

Product Information
MicroFEM modeling features

saturated flow, single density
multiple-aquifer systems and stratified aquifers
confined, leaky and unconfined conditions
steady-state and transient flow
heterogeneous aquifers and aquitards
spatially and temporally varying wells and boundary conditions
spatially varying anisotropic aquifers
hydraulic heads and water balances
2-D and 3-D flowlines with travel times

DOS System Requirements

IBM-compatible computer
DOS operating system
VGA, EGA screen
color monitor recommended
coprocessor recommended
extended memory recommended
Program Features and Capabilities

graphical user interface
easy data manipulation
interactive assignment of spatially varying properties
interactive visual error checking
up to 16 aquifers or sublayers
up to 12.500 nodes for each layer
mesh generator for regional flow models
high contrast mesh generator for civil engineering models
interactive mesh design and adjustment
user assigned names for all nodes
any number of wells
flow vectors and flowlines, 3-D particle tracking
water balances for each aquifer, subarea and time step
transferring existing model properties to a new mesh
transient flow modeling in batch or command mode

Program parts

To allow the largest possible models to run on a microcomputer, making full use of the computer's memory, the modeling procedure has been split up into several well-defined parts and related programs. The core of Micro-Fem consists of FeModel, a fully interactive graphics input/output program with a built-in calculation module.

Program:Description:
FemGridThe program FemGrid is a mesh-generating program within Micro-Fem. It generates a triangular irregular network with variable spacing, based on a subdivision of the area into irregular polygons with uniform internal node-spacing. FemGrid is suitable for irregular geometries which are often encountered in regional studies (e.g. meandering rivers).
FemMeshThe program FemMesh is an alternative mesh-generating program within Micro-Fem. Like FemGrid it also generates triangular irregular networks with variable spacing. FemMesh is based on a subdivision into triangular and quadrangular areas with gradually changing nodespacing. FemMesh is useful for problems which require high contrasts in spacing (for example, sheet piling or excavations).
FeModelThe core of Micro-Fem consists of FeModel, a fully interactive graphics input/output program with a built-in calculation module. As a preprocessor it offers the possibility to add and (re)move nodes at any time and it allows the graphical, interactive input of model-parameters. 
The postprocessing capabilities include all kinds of contour maps, flow-vectors, flowlines and water budgets
FemInvsThe program FemInvs was developed to automatically calibrate steady-state models (inverse modeling). The program adjusts the selected model input data to reduce the differences between observed and computed heads. The model may consist of 16 aquifers and EM version can handle up to 12500 nodes. Anisoptropy in all layers is allowed.
FemCat & FemCurvThe program FemCat handles transient calculations. A FeModel-file with the initial conditions and files with the storativities for each aquifer must be prepared. One or more time periods and the number of time steps can be specified. 
The program FemCurv visualizes the time-head files written by FemCat. Time-head or drawdown curves and time-distance profiles with various drawing options are among the possibilities. It also writes HPGL-files that can be plotted or imported by wordprocessors. 
FemPath & FemProfThe program FemPath is a three-dimensional particle tracking program which interprets a FeModel-file using additional aquifer and aquitard thickness data. Flowlines run forward or backward, starting at any node, in any aquifer and at any depth. The number of flowlines is unlimited. Fempath can be activated from FemCat to create coupled steady-state and transient pathlines. The program FemProf draws isohypses and flowlines in a vertical cross-section. 
FemPlotThe program FemPlot plots map views, generated by FeModel and by FemPath, and writes HPGL and DXF-files. 

Inner workings of the modeling procedures

The modeling procedure consists of the following parts:

Finite element grid generation
Preprocessing
Steady-state modeling
Postprocessing
Transient modeling
Plotting and interfacing
Automated calibration

Finite element grid generation

FemGrid and FemMesh are the mesh generating programs of Micro-Fem. Both make triangular irregular networks with variable spacing. 
FemGrid generates a mesh based on a subdivision of the area into irregular polygons with uniform internal node-spacing. FemGrid is suitable for irregular geometries which are often encountered in regional studies (for example, meandering rivers). 
FemMesh is based on a subdivision into triangular and quadrangular areas with gradually changing node-spacing. FemMesh is useful for problems which require high contrasts in spacing (e.g. sheet piling or excavations).

Preprocessing

FeModel is both the pre- and the postprocessor of Micro-Fem. As a preprocessor it offers the possibility to add, move and remove nodes at any time and it allows the graphical, interactive input of model-parameters. You "walk" from node to node with the arrow keys and enter or change model parameters on the fly. You can also define an area by "walking and marking" along its boundary. It is possible to enter labels and parameters for a node, a group of nodes, an area or the whole model at once. FeModel is able to assign values to the model parameters by evaluating functions and expressions; a wide variety of variables and standard functions is incorporated. Interesting possibilities arise by making values a function of distance or position. To check the entered data FeModel draws colored maps of the model parameters and shows the minimum and maximum values on the screen.

Steady-state modeling

Both FeModel and the stand-alone finite-element program FemCalc can calculate the steady-state heads and prepare results for postprocessing by FeModel or FemPath. Generally calculation times are short: a steady-state model of moderate size (e.g., three aquifers and 4000 nodes) takes less than 1 minute on a 66 MHz 486-type PC.

Postprocessing

FeModel's postprocessing capabilities include fast and easy construction of maps of flow-vectors, heads, drawdowns and the vertical flow components for every aquifer. Flowlines can be drawn up- and downstream, indicating travel times. Water balances can be computed for any selected node or area of the model. The FeModel options will be adequate for those occasions where only the distribution of heads and water balances are the objective of the modeling study.

Transient modeling

Transient calculations are handled by FemCat. 
A FeModel file with the initial conditions and files with the storativities for each aquifer must be prepared. One or more time periods and the number of time steps for each period can be specified. At each timestep FemCat allows changes in pumping, boundary heads and all other parameters. The number of time periods is unlimited. For selected nodes heads can be saved in a special file for each time step. FemCat also offers the user other features: in phreatic aquifers seepage to surface water can be modeled, and after each time step transmissivities can be adjusted to the calculated height of the water table. 
Anisotropic transmissivities can be incorporated for each node and each aquifer. 
FemCurv is the program that visualizes the time-head and flux data written by FemCat. Time-head or drawdown curves and time-distance profiles with various drawing options are among the possibilities. It also writes HPGL-files that can be plotted or imported by word processors.

Plotting and interfacing

Graphical output from all Micro-Fem programs can be plotted on a HP-compatible plotter or translated to HPGL or DXF graphics files by FemPlot. FeModel and FemPath save different types of ASCII-files with model data for easy interfacing with geographic information systems (GIS) and database programs. FemCat files can also be loaded by a spreadsheet program.

Automated calibration

FemInvs was developed to automatically calibrate steady-state models (inverse modeling). The program adjusts the selected model input data to reduce the differences between observed and computed heads. The model may consist of 16 aquifers and can handle up to 12.500 nodes. Anisotropy in all layers is allowed. Since hydraulic properties usually vary from node to node and since the number of parameters to be optimized is limited to 40, it is not the hydraulic properties themselves that are calculated, but rather the corrections to these properties. For each parameter a subarea has to be selected for which the correction will be computed. When referring to a transmissivity, a hydraulic resistance or a discharge, the correction is a multiplication factor that is applied to all values in the selected area; when fixed heads are optimized, the correction is added to the original model heads.

Screenshot

screenshot

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