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Question
How can I represent a fracture in FEFLOW?

Answer
Discrete Features can be added to models to represent highly conductive one- or two-dimensional features, for example, tunnels, drains, faults or fractures. Discrete Features can be assigned along element edges (1D), element faces (2D), or they can connect two arbitrary nodes within the mesh.

The workflow and steps to create Discrete Features are:

#01 - In the Selection Toolbar, activate the target geometry for Discrete Feature assignment (Slice or Join Edges, Slice or Join Faces, Nodes for arbitrary discrete features) - see Fig. 1

Fig. 1 - Selection of toolbar options


#02 - Use one of the selection tools of the Selection Toolbar to activate and create the selection - see Fig. 2 as example of 1D Discrete Feature element

Fig. 2 - Selection for 1D Discrete Feature

#03 - To add discrete features at the selected location, go to the Discrete Features panel, open the context menu of Discrete Features and select Add...Feature Element and the preferred flow law - see Fig. 3

Fig. 3 -Discrete Feature panel while creating a Discrete Feature from a selection
 

#04 - The Discrete Feature is now added to the Discrete Features panel as "Feature 1". It will also appear as a new subfolder in the Data panel under Discrete Features that contains the specific parameter options of the Discrete Features, as shown in Fig. 4. The chosen flow law and geometry type are displayed behind the feature's name.

Fig. 4 - Discrete Feature and Data Panels after the creation of the Feature


#05 - To show the Discrete Features in the active view, double-click on one of the discrete-feature properties in the Data panel.

#06 - To edit a Discrete Feature parameter, set this parameter to active with a double-click in the Data panel. To select all edges/faces belonging to the desired Discrete Feature, double-click on the feature's name in the Data panel.

#07 - Use Assign Values or Maps assignment mode to edit the parameter values. The flow law can be changed using Change Law in the context menu of the feature's name in the Data panel.

#08 - To create an Arbitrary Discrete Feature, the option "Select Arbitrary Node Path" is available in the Selection Toolbar - see Fig. 5

Fig. 5 - "Select Arbitrary Node Path"

In this case, only the nodes at the ends of the Discrete Feature must be selected, and they need to correspond to mesh nodes - see Fig. 6. Be aware that only the selected nodes will exchange mass and fluid with the model domain.

Fig. 6 - Selected nodes only will exchange mass and fluid with the model domain

FURTHER INFORMATION & USEFUL LINKS
FEFLOW 7.5 Documentation - Discrete Feature Elements

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