## TRANSIENT

Additional module for SS-FLOW2D for transient groundwater flow in two-dimensional groundwater systems.

Calculation of non-steady-state groundwater flow.

Program Capabilities:

- Consideration of seepage lines and the unsaturated zone
- Graphically oriented data input and change of time-dependent boundary conditions using polygons for potentials and flux
- Graphically oriented data input and change fixed boundary conditions using polygons for potentials and flux (single, line and area flux)
- Color supported presentation of potentials in cross-section
- Presentation of potentials as progress line for selected system nodes
- Time oriented presentation of velocities, flux, flow lines or potentials as normal, colored or 3-dimensional Iso-lines
- Animated screen presentation of potentials over time
- MiniCAD-System for additional labelling and illustationFor a transient calculation of groundwater flow, a stable initial condition is required. This initial condition is found by the program TRANSIENT from a file (e.g. PLGW.DA1) which is created from a previous analysis undertaken with the program SS FLOW 2D. This data must be loaded as the first action after starting the program. In addition to the analysis results, the data file also contains the relevant soil and input parameters for the analysis.These fundamental parameters (e.g. k, neff etc.) cannot be modified in the TRANSIENT program. If they are altered, then the soil parameters will no longer match the potentials and flows, and the transient calculations will be meaningless.Of course, for all groundwater flow problems (planar vertical, planar horizontal and axisymmetric), it is necessary to input parameters which are appropriate for a transient flow calculation.In addition to soil parameters, time-dependent boundary conditions can be defined for the transient program. Time dependent boundary conditions (potential or flow) are entered as polynomial functions. These polynomial functions can be defined at single or multiple system nodes. These (transient) soil parameters and polynomials can be saved in a separate boundary data file, to be available for a subsequent calculation.Boundary conditions that were defined in the course of the SS FLOW 2D calculation, are automatically saved in the input data file (e.g. PLGW.DA1). These are assumed to be constant for the duration of the calculation in TRANSIENT, unless they are specifically cancelled in the program TRANSIENT. The program TRANSIENT allows one to view the initial static conditions (e.g. PLGW.DA1) on the screen to enable confirmation that the correct system is being solved.
The TRANSIENT program is not able to display the transient results. The output program PLGW is available for this purpose.

System requirements

Software runs on PCs with the following specifications:

• Pentium I or higher processor

• minimum 32MB memory

• Microsoft Windows 2000, XP, Vista

• 10MB free hard disk space

• CD-ROM drive (for installation)

• VGA or higher resolution monitor