GMS:FEMWATER Conceptual Model Approach: Difference between revisions

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A FEMWATER conceptual model is used to build a numerical model using a two step process. In the first step, a 3D mesh is created. This can be done by using the feature objects in conjunction [[#Building the 3D Mesh from the FEMWATER Conceptual Model|with a set of TINs to build a 3D Mesh]] or a solid can be converted to a layered 3D Mesh using the [[GMS:Solids to Layered Mesh|'''''Solids -> Layered Mesh''''']] command. In the second step, the boundary conditions and recharge values assigned to the feature objects are automatically assigned to the appropriate nodes and element faces of the 3D mesh using the '''''Feature Objects | Map -> FEMWATER''''' command.
A FEMWATER conceptual model is used to build a numerical model using a two step process. In the first step, a 3D mesh is created. This can be done by using the feature objects in conjunction [[#Building the 3D Mesh from the FEMWATER Conceptual Model|with a set of TINs to build a 3D Mesh]] or a solid can be converted to a layered 3D Mesh using the [[GMS:Solids to Layered Mesh|'''''Solids -> Layered Mesh''''']] command. In the second step, the boundary conditions and recharge values assigned to the feature objects are automatically assigned to the appropriate nodes and element faces of the 3D mesh using the '''''Feature Objects | Map -> FEMWATER''''' command.


To create a FEMWATER conceptual model right click on the Map Data folder in the [[GMS:The GMS Screen|Project Explorer]] and select the '''''New Conceptual Model''''' command.  In the Conceptual  Model Properties dialog change the model type to FEMWATER in the pull-down list.  In the dialog the simulation options of flow and transport can also be toggled on or off. Next create a [[GMS:Coverages|coverage]] by right clicking on the FEMWATER conceptual model in the data tree and selecting '''''New Coverage'''''.  The coverage attributes can  then be setup in the '''Coverage Setup''' dialog.   
To create a FEMWATER conceptual model right click on the Map Data folder in the [[GMS:The GMS Screen|Project Explorer]] and select the '''''New Conceptual Model''''' command.  In the Conceptual  Model Properties dialog change the model type to FEMWATER in the pull-down list.  In the dialog the simulation options of flow and transport can also be toggled on or off. Next create a [[GMS:Coverages|coverage]] by right clicking on the FEMWATER conceptual model in the data tree and selecting '''New Coverage'''.  The coverage attributes can  then be setup in the ''Coverage Setup'' dialog.   


A FEMWATER coverage can contain points, arcs, and polygons. The points are  used to define wells, the arcs are used to define boundary conditions, and the  polygons are used to define recharge zones. In most cases, a single coverage is  sufficient. However, multiple FEMWATER coverages can be used if desired.
A FEMWATER coverage can contain points, arcs, and polygons. The points are  used to define wells, the arcs are used to define boundary conditions, and the  polygons are used to define recharge zones. In most cases, a single coverage is  sufficient. However, multiple FEMWATER coverages can be used if desired.

Revision as of 22:42, 15 February 2012

FEMWATER
Meshgenc.png
Pre-processing
Building a FEMWATER Model
FEMWATER Model Input
Saving a FEMWATER Simulation
Post-processing
FEMWATER Display Options
FEMWATER Post-Processing Viewing Options
Tutorials
FEMWATER Tutorials
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The preferred method for setting up a FEMWATER simulation is to use the feature object tools in the Map module to define a FEMWATER conceptual model of a site being studied. The conceptual model is a high-level description of the site including sources/sinks, the boundary of the domain to be modeled, rainfall and seepage zones, and material zones within each of the layers. The conceptual model is defined with feature objects, including points, arcs, and polygons, and is constructed independently of a numerical grid. Once the conceptual model is complete, a mesh is automatically constructed to fit the conceptual model, and the FEMWATER data are converted from the conceptual model to the nodes, elements, and element faces. The dialogs and interactive editing tools in the FEMWATER menu can then be used to edit or review the data if desired.

A FEMWATER model can be created in GMS using one of two methods: assigning and editing values directly to the nodes and elements of a mesh (the direct approach), or by constructing a grid-independent representation of the model using feature objects and allowing GMS to automatically assign the values to the nodes and elements (the conceptual model approach). Except for simple problems, the conceptual model approach is typically the most effective.

The conceptual model approach utilizes feature objects in the Map module. A FEMWATER conceptual model is created in the Map module and feature objects are used to create a high level representation of the site you are modeling. The figure below shows a sample conceptual model.

File:Samp map.gif
Sample FEMWATER Conceptual Model

Two Step Process

A FEMWATER conceptual model is used to build a numerical model using a two step process. In the first step, a 3D mesh is created. This can be done by using the feature objects in conjunction with a set of TINs to build a 3D Mesh or a solid can be converted to a layered 3D Mesh using the Solids -> Layered Mesh command. In the second step, the boundary conditions and recharge values assigned to the feature objects are automatically assigned to the appropriate nodes and element faces of the 3D mesh using the Feature Objects | Map -> FEMWATER command.

To create a FEMWATER conceptual model right click on the Map Data folder in the Project Explorer and select the New Conceptual Model command. In the Conceptual Model Properties dialog change the model type to FEMWATER in the pull-down list. In the dialog the simulation options of flow and transport can also be toggled on or off. Next create a coverage by right clicking on the FEMWATER conceptual model in the data tree and selecting New Coverage. The coverage attributes can then be setup in the Coverage Setup dialog.

A FEMWATER coverage can contain points, arcs, and polygons. The points are used to define wells, the arcs are used to define boundary conditions, and the polygons are used to define recharge zones. In most cases, a single coverage is sufficient. However, multiple FEMWATER coverages can be used if desired.

More on point/arc properties here: FEMWATER Point / Arc Properties

Build a 3D Finite Element Mesh

Once the FEMWATER conceptual model is constructed, the next step is to use the conceptual model to build a 3D finite element mesh. This is accomplished by first building a 2D mesh, then building the 3D mesh by extruding each of the 2D elements in 3D elements.

Map -> 2D Mesh
File:Meshgenc.gif
Converting a FEMWATER Conceptual Model (a) Conceptual Model (b) 2D Mesh Created with Map -> 2D Mesh Command (c) 3D Mesh Created by Extruding 2D Mesh (d) 3D Mesh after Map -> FEMWATER Command.

The first step in building the 3D mesh is to select the Feature Objects | Map -> 2D Mesh command. This command creates a 2D mesh by automatically filling in the interior of the conceptual model with nodes and elements. The size and spacing of the elements is controlled by the spacing of the vertices on the arcs and by the refine point attribute assigned to any wells in the interior of the conceptual model.

An example of the Map -> 2D Mesh command is shown in the following figure. A sample FEMWATER conceptual model is shown in part a. The 2D mesh resulting from execution of the Map -> 2D Mesh command is shown in part b.

Creating the 3D Elements

Once the 2D mesh is created, the next step is to create the 3D mesh by extruding each of the 2D elements into a series of 3D elements. The elevations of the 3D elements can be defined from a set of boreholes, a set of TINs, or a set of Solids.

For sites with relatively simple stratigraphy, the Regions -> 3D Mesh command in the Borehole module can be used.

For sites with more complex stratigraphy, the TINs -> 3D Mesh command in the TIN module should be used.

A mesh can also be created using the Solids -> Layered Mesh command in the Solid module.


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