Example Applications of FEMWATER-GUI
Areal Ground-Water-Flow Model
This example shows how to create an areal steady -state ground-water- flow model (ignoring solute transport), run FEMWATER, display simulation results, and save the project for use in subsequent step-by-step examples.
Assume that there are four lakes, one at each corner of a closed alluvial valley. The lakes control the hydraulic head at each corner, and no flow crosses the bedrock sides of the valley. A hydraulic head value will be specified where each lake exists. Assume that three of the lakes are at the same elevation, which is somewhat higher than the fourth lake.
Entry of Hydrogeologic Data
- Double-click on the Argus ONE icon. This opens Argus ONE.
- From the PIEs menu found along the top of the window, select New FEMWATER Project… This brings up the Model Configuration pane of the FEMWATER Project Information dialog box.
The Model Configuration pane is where the type of problem to be simulated is chosen. To select the default type of AREAL, click on Continue. This sets up a problem of areal flow with constant-density solute transport using an irregular finite-element mesh.
The other panes allow the user to specify values for the FEMWATER simulation that are not spatially variable; that is, those that may have only a single value, such as “time step.” These may be inspected on the various panes by clicking on the list of panes on the left. Rather than making changes here now, accept the default values by clicking OK. This brings up a new Argus ONE window, called “untitled1.”
The default values set up simulation of steady-state ground-water flow in a sandy-type aquifer.
In the FEMWATER dialog, click on the Boundary Conditions|Dirichlet tab to activate fixed head profile type by clicking Fixed Head check box and then click Add Rows button to add the number of profile. Set the profiles as follows:
N Time 1 Head 1 Time 2 Head 2 1 0.0 0.0 1.0e38 0.0 2 0.0 10.0 1.0e38 10.0
The Argus ONE window is where the model will be designed, run, and evaluated. It contains many layers in a stack; each layer will hold either model or mesh information. Additionally, another window, the Layers’ Floater can be shown by clicking on the Layers button . It allows users to see which layers are available. This window may be resized to display the full layer names.
The Layers’ Floater shows which layers are available for the particular problem type (AREAL) chosen in step 3. It allows the user to control which of the layers will be visible (those with the open eye ) and which layer is active and thus available for input from the screen. Clicking on an “eye” toggles the layer visibility. (The icon changes to a closed eye .) Clicking to the left of an “eye” makes the layer active and puts a check mark next to it.
One way to begin a modeling project is to enter hydrogeologic information for the area into the appropriate geospatial Information layers provided in FEMWATER-GUI. The layers listed in the Layers’ Floater (for example, Soil Properties, and Hydraulic Conductivity) have already been assigned default values by the interface (these values are shown in two figures below). Rather than modify any of these values, in this step-by-step example, the defaults will be accepted. A situation will be considered in which only boundary conditions need be assigned to make a model.
To specify a constant elevation, or default elevation for the nodal of layer, the Layers dialog must be used. Moving the cursor to the Layers… button in the floating layers window and clicking, opens the Layers dialog. The list at the top of the dialog is the list of layers (figure below).
Highlighting the layer under consideration, in this case Nodal Elevation Layer2, in that list by clicking it with the cursor shows the parameters associated with that information layer in the table at the bottom of the dialog box. Moving the cursor to the Value column and clicking fx the expression box to appear (figure below). Just type 10 in the expression box and clicking OK exits the expression dialog.
Draw a lake by first activating the contour-drawing tool Then move the cursor into the white workspace and click at three locations, creating the first vertices of a closed contour. Try to create a lake similar to one of the four shown in following figure.
Then, double-click on the location desired for the last vertex. The Contour Information dialog box appears.
- The fixed head value of water potentially entering the aquifer from the lake must be specified in the dialog box. This is done by clicking next to Fixed Head Prof Type (below Value) and entering the profil type, then clicking OK. For the first lake, specify 2 for the second profil type. For this step-by-step example, all the lakes contain no solute.
- Draw the other three lakes by clicking to create small closed regions similar to the ones shown in figure above. For each lake, double-click on the last vertex to close the shoreline. This brings up the Contour Information dialog box for each lake. For two of the remaining lakes, enter 2 for the second profil type, and for the last lake, enter 1 for the first profil type.
This completes entry of hydrogeologic data for simulating ground-water flow in this system.
- Now draw the model boundary. Make the Domain Outline layer active by clicking to the left of its “eye” in the Layers’ Floater. This makes the FEMWATER Domain Outline layer active, although the Fixed Head Prof Type layer remains visible. The purpose of the Domain Outline layer is to contain model boundary locations. The model boundary will follow the valley walls and the corners will be placed at the center of the lakes.
Draw a model boundary by first activating the Domain-Outline-drawing tool . Then move the cursor into the white workspace and click in the center of one of the lakes. Proceeding around the workspace, click at the center of each lake. Try to create a domain outline that looks like the one shown in figure below. Then, double-click at the center of the last lake to close the model domain contour.
- The Contour Information dialog box appears. In it, specify the desired typical size of finite elements to be created by the mesh generator is specified. Type 0.5 in the space below the label, Value. This sets the desired width of an element to 0.5 in the units shown in the rulers around the periphery of the workspace. The result should look similar to the model boundary shown in figure above. Click OK to exit the dialog box.
- Next, the finite-element mesh will be created. Activate the FEMWATER QuadMesh layer by clicking to the left of its “eye” in the Layers’ Floater.
Click on the ‘magic wand’ and then click the magic-wand cursor inside the model boundary just drawn. An irregular finite-element mesh containing elements with a size of about 0.5 is generated and displayed. Figure below shows the type of mesh that may be expected.
- The bandwidth of a newly generated irregular mesh always needs to be reduced. Select the Special|Renumber… This brings up the Renumber dialog box. Click on Optimize Bandwidth and then OK. The mesh numbering is then optimized for the matrix solver currently used by FEMWATER.
The entry of data and preparation of the mesh for simulating ground-water flow in this system is now completed.
- Save the project so far by selecting File|Save As… menu item. Select the desired directory and type in the desired name (for example, “Areal-F” for areal flow model) and then click on Save. A project file called Areal-F.mmb is created in the directory chosen by the user, and the window name becomes the same, as shown in figure above.
- The model information now needs to be exported from Argus ONE creating input files that FEMWATER requires, and the simulation can then be run. (Note: the FEMWATER QuadMesh layer must be active to export.) Select PIEs|Run FEMWATER. The Run FEMWATER dialog box appears.
- This dialog box allows the user to choose only creation of FEMWATER input files, or creation of files and running of FEMWATER (the default). Click OK to proceed. An Enter export file name dialog box appears.
- Select the directory into which the FEMWATER input files will be placed by Argus ONE. Then select the name of the files by typing in the space next to File Name (for example, “Areal-F.inp”). The files created will all begin with the name entered here and the suffixes will be appended.
- Click on the Save button and the export takes place while the barber pole is visible, and then the FEMWATER simulation is run while the DOS window is visible. If requested, hit any key to exit the DOS window. Now, the completed FEMWATER simulation has created output files in the directory that was selected.
- To display the results, select PIEs|FEMWATER 2D Post Proc… An Open File dialog box appears in which the user can select the data set files produced by the model. Click Select Data Set.
- Find the directory selected above for the FEMWATER files and double-click the appropriate file. This brings up the FEMWATER Post Processing results to display dialog box.
- Because the FEMWATER QuadMesh layer was active, the mesh hides the plots. To make them visible, activate the FEMWATER Post Processing Charts layer (click left of the “eye” for that layer in the Layers’ Floater).
- The plot appears, but the window is too cluttered because the mesh is also visible. Make the mesh invisible by clicking on the ‘eye’ next to FEMWATER QuadMesh in the Layers’ Floater.
- Save the current state of the project by selecting File|Save.
- The Argus ONE application may now be closed by selecting File|Quit. When the project is reopened, it will be in the same state as when it was closed.
This dialog box contains a list of all results available from the FEMWATER simulation for visualization. Because the simulation was for steady-state conditions, only one time step appears. Also, select a velocity vector map by changing the no below Velocity to YES. Then click on OK and the plots of velocity vectors and head contours (similar to that in figure below) are created.
Ground water flows into the aquifer from three of the lakes and exits at the fourth lake. Hydraulic head in the aquifer decreases near the outflow lake.