Utility (UTIL) Module: FFTools Plug-In

Description

The Utility (UTIL) Module can record, in external files, several types of information that FEFLOW may not report:

Element-based volumes of stored fluid: The contributions of S_s and S_y are estimated as a summary value for the entire model. FEFELOW currently reports contributions from these two sources as one value in its Content, Rate Budget, and Period Budget panels.
Nodal water-table elevation; currently this must be computed using information stored in a DAC file (a number of methods are possible but there are no direct methods of exporting this information on a node-by-node basis).
Nodal head, saturation, and pressure information.

At every time step these options save data to a user-defined ASCII output file. The external files can grow exceptionally large (possibly exceeding the size of the FEFLOW DAC file). Writing these files will increase model run time (up to approximately 10% longer on typical desktop PC hard drives). Nevertheless, a user may find these tools handy for certain situations.

Suggested FEFLOW Configuration

The UTIL module has been tested on models with the following characteristics:

FEFLOW versions 7.x
Three-dimensional mesh using layered prismatic elements (prismatic elements having a triangular shape in horizontal cross section)
All slices set to "fixed" in FEFLOW's "3D Layer Configuration..." editor
FEFLOW Problem Class: Richard's equation for variably-saturated media
State: Transient

Storage Calculations

In FEFLOW budget calculations (Rate, Period and Content panels), storage of fluid volume is reported as a combined value of the Ss and Sy components. In some cases, it is useful to separate the two components and enabling this option will save the S_s and S_y components for every element at the end of every timestep.

Water-Table Elevation

With this option, the elevation of the water-table is reported for each slice 1 node (XY position). To find the simulated water table at a particular XY node location, the tool starts at that XY location on slice 1 (the top-most slice), and works downward through all slices until the first fully saturated node is found on a slice directly below the current XY position. Once this node is found the elevation (head) of the water table must be computed. This is done using a linear interpolation between the head at the fully saturated node and the head at the node directly above the saturation = 1.0 node. Note that if the node at the current XY location on the top slice is fully saturated, the "water table" equals the head at that node (a water level above the top of the model implies a confined condition; no water table exists at that XY location). If none of the nodes in a vertical column at an XY location are fully saturated, the tool will report the bottom elevation of the model as the water-table elevation; a value must be reported and there is no other information to base an estimate. In addition, this tool does NOT identify multiple water tables at a single XY location; it only reports the elevation of the highest water table, which could be a perched water table.

The result is a 2D listing of water table elevations with the corresponding surface (slice 1) node number. Results are saved at every time step.

List Simulation Results at Nodes

This option allows the user to save simulated head, pressure, and saturation at every time step in cases where the user does not direct FEFLOW to save a complete DAC file. The user then has data available for further post-processing and analysis by importing the saved data into FEFLOW data arrays or into other software.

Setup

All setup is managed through the UTIL setup tab which is accessed by right-clicking on the FFTools entry in FEFLOW's "Plug-ins" panel and selecting "Edit...":

Figure 1: UTIL Setup Tab.