GGU-CONTAM-RW: Short description

Since I know from personal experience that reading user-manuals is quite a chore, there will now follow a short description of the main program functions. After studying this section, you will be in a position to model contaminant transport based on steady-state groundwater flow. You can learn about the details of the program in the subsequent chapters.

• In order to be able to use the system entered in your GGU-2D-SSFLOW groundwater flow program for contaminant transport modelling using the GGU-CONTAM-FE program, you must create a file in the GGU-2D-SSFLOW program with the file extension ".da1". You can create this file by going to "System/Analyse" and activating the check box "Generate record for transient modelling".

• Start the GGU-CONTAM-RW program and using the menu item "File/Load GW data", select the desired record of a flow system.

• Using the "Editor" menu you can define your "Soil properties". A description of the individual constants can be found in the "Info" function field.

• The initial concentrations and any concentration sources are defined using the "Concentrations" menu. This is possible individually or in a section. You will be shown an info box with instructions. After being queried on whether you want to assign or delete concentrations, a dialog box opens in which you must define whether it is an initial concentration or a concentration source. In the first instance, the concentration only applies at time t = 0 and is subsequently displaced, whilst a concentration source displays a constant concentration. If you do not define an initial concentration or a concentration source for any nodes, an initial concentration of "0" will be assumed.

• In "Modelling/Preferences", you can apply preferences for the precision and extent of analysis by specifying the size of the array subdivisions. The smaller the array is defined, the more precise, but also time-intensive, the analysis. Moreover, by activating the analysis with the "Element velocities" option and deactivating the "Exact velocities" box you achieve fast, but less precise, analysis, whilst modelling using node velocities and the additional option of "Exact velocities" will give very precise analysis results.

• Commence contaminant transport modelling for your groundwater system with
  "Modelling/Start". In the dialog box that then opens you can enter the name of the output file for the rectangular array, as well as generating a record for the FEM mesh if you want an additional analysis based on the triangular array. The program then calculates several basic parameters. You then define an end time, the size of the time steps and the number of particles. A large number of particles also means more precise results but longer computing time.

• With the aid of the GGU-PLGW evaluation program, you can evaluate and display the modelling results. To facilitate this, load the file generated by GGU-CONTAM-RW ("_ras.plw") or the file ("_fe.plw") with the results recalculated based on the FEM mesh in GGU-PLGW.