Except for TOUGH-Fx/HYDRATES, all the TOUGH executables are included as an integral part of the PetraSim software. To execute the appropriate TOUGH module, on the Analysis menu, click Run TOUGH2 or click . This will first save the PetraSim model file and then the TOUGH2 Simulation Run dialog will be displayed, Figure 12.1.

The Running TOUGH2 dialog displays simulation time steps on the X-axis and the log10 of the time step on the Y-axis. As a rule of thumb, an increasing Y value is a good sign of simulation progress. If your time steps start to become smaller, it may indicate that the simulator is having a difficult time converging.

When the simulation finishes, a message will be displayed and the Cancel button will turn into a Close button. Click the Close button.

Figure 12.1. Running the TOUGH analysis

A TOUGH analysis makes heavy demands of the computer processor; if you are running a single core computer, you may want to reduce the priority of the TOUGH analysis. Start the Task Manager (Cntrl+Alt+Delete or right-click on the lower toolbar). On the Processes tab, click on CPU to sort by the process using the most CPU (you many need to click twice to bring highest CPU users to the top of the list). You will see a process such as "EOS7.exe". Right-click on the process, select Set Priority and select Low. Close the dialog.

Setting the priority low will keep your computer response snappy to other tasks and allow the CPU to support the TOUGH analysis when not needed for other tasks.

During the TOUGH analysis, there are several ways to monitor progress. One way is to go to the problem directory and, using a text editor, open the *.out file as it is written by TOUGH. In this file will be text similar to the following:

    
  ********************************************************
     260(  21,  3) ST = 0.209715E+09 DT = 0.104858E+09
     365(  22,  3) ST = 0.419430E+09 DT = 0.209715E+09
      51(  23,  4) ST = 0.838861E+09 DT = 0.419430E+09
     216(  24,  4) ST = 0.125829E+10 DT = 0.419430E+09
     258(  25,  4) ST = 0.167772E+10 DT = 0.419430E+09
    

The first number is the ID of the cell with the smallest time step. The first number in the parantheses is the time step counter and the second number is the number of iterations required for that step to converge. ST is the total solution time. DT is the solution time increment.

Most users will not need to explicitly save a TOUGH input file, since this is automatically written when the analysis is performed. However, if you are using TOUGH-Fx/HYDRATE or if you have a special TOUGH executable, you can select File->Wrute TOUGH2 File... to write the standard TOUGH input file. This file can then be edited (if necessary) and used to run your special TOUGH executable from the commmand line. Save the output to filename.out (where filename is the name of the PetraSim file) and you can then read the results for plotting in PetraSim.