FEFLOW | Representing Buildings and Hydraulic Barriers with Deactivating Elements

MODELING TASK DESCRIPTION

Model domains sometimes contain natural or anthropogenic structures that are hydraulically inactive, for example solid rock sections, underground constructions, tunnels or sheet walls. However, FEFLOW is a continuum model and cannot represent hydraulic discontinuities from one to an adjacent element. To prevent flow through element groups or subdomains, FEFLOW uses the concept of element deactivation. If elements are deactivated, no equations are solved for the affected nodes and no flow occurs here. 

SOLUTION
The user defines which element groups of the model domain are inactive and for which time-period. The de-/activation can be controlled by timeseries.

NOTE: The definition of In-/active Elements can be applied to phreatic, fully confined or Richards' Equation models, but not to a Free and Movable Surface!

The procedure of inactivating elements is as follows:

Option #01 - for steady-state models

Go to In-/activate Elements in the Data Panel and select the element you wish to set inactive and assign it accordingly - see Fig. 1.

Fig. 1 - Data Panel->  In/activate Elements option and the selected specific elements highlighted
 

Option #02 - for transient models

If your barrier is dynamically de-/activated , open the context menu of the parameter with a right-click and choose Make Transient - see Fig. 2.

Fig 2 - Make transient the in/activate Elements

Add the time-stages, when the parameter needs to switch between active or inactive. In the dialog below, you can add the list of Time Stages - see Fig 3.


Fig. 3 - Add time stages 



Once you click on OK, you can move to the correct time (using forward/backward toolbar in the Slice View) and assign the parameter value - see Fig. 4 and 5.


Fig 4 - Assign the parameters to the correct time stages

Fig. 5 - Time-dependent In-/active Elements

 

Alternatively, you can also describe the In-/active Elements time dependency via a normal time-series (0: inactive and 1: active) - see Fig. 6. The time-series can be assigned to the parameter as for any other time-varying Material Property or Boundary Condition.


Fig. 6 - Time-series defining the in-/activation of Elements 

FURTHER INFORMATION & USEFUL LINKS

Manuals and Guidelines
FEFLOW 10.0 Documentation - Assignment of time-varying Material Properties
FEFLOW 10.0 Documentation -  FEFLOW Time Series
FEFLOW 10.0 Documentation - Time Series Editor