1.2.9. Executing Tdyn Solver

1.2.9.1. Automatically executing tdyn

Tdyn CFD+HT solver can be comfortably started through Tdyn pre-processing environment Calculate menu. Once the analysed problem is defined (i.e. the geometry is created) the boundary conditions assigned, and the mesh is generated, the Start button in the Calculate menu (or the Calculate icon) can be pressed.

When the Start button is pressed, the system writes the input file for the calculation module (the ‘calculation file’) called ProblemName.flavia into the ProblemName.gid directory, and then the compassfem.tdyn?d.win.bat file from the Tdyn problemtype directory is executed, with the following arguments:

Argument 1: Problem name Argument 2: Problem directory Argument 3: Problemtype directory

From within the compassfem.tdyn?d.win.bat batch file, the program executable tdyn.exe is called, with the name of the input file given as an argument. Now tdyn.exe is started and creates a number of output files (see Output files) section for a brief description of the files generated during the execution).

1.2.9.2. Manually executing tdyn

Sometimes it can be interesting to run the Tdyn executable manually (without using the graphic user interface of the software). The necessary steps are described here.

From here in advance, the following notation will be employed for description purposes:

$gidpath : root directory of the installed program. It contains, among others, the gid.exe executable file called to run the GiD custom GUI.

$CompassFEM_version : CompassFEM problemtype version name.

$inputpath : directory that contains the tdyn input data file.

$modelname : name of the input data file.

First, the input data file required by the Tdyn executable must be generated before execution. To this aim, the corresponding model must be loaded to the GiD custom interface.

Next, the input data file must be exported, assuming that the model setup has been finished successfully (applying material properties and boundary conditions) and that the mesh has been already generated. In order to export the input file, the following menu sequence must be used:

Files > Export > Calculation file…

By doing this, the user will be asked for a file name ($modelname) and location ($inputpath). By default, .dat extension will be used to export de input file. If desired, .flavia extension can be also specified for instance, trying to mimic the file name convention used when running Tdyn automatically.

Before execution, you must ensure that the tdyn process is able to find a password.txt file containing a valid tdyn password. You can create such a text file manually and copying the password inside. Alternatively, the password.txt file can be copied from the directory $gidpathproblemtypes$CompassFEM_versioncompassfem.gid , where it is automatically saved if tdyn passwords have been previously registered through the GiD custom GUI. For manual execution of tdyn, the password file must be located either next to the tdyn.exe executable (this is on the previously mentioned $gidpathproblemtypes$CompassFEM_versioncompassfem.gidexec directory) or next to the input file.

After exporting the input file and copying a valid password.txt file, everything is ready to launch tdyn manually. To this aim, open a command shell and move to the location of the tdyn.exe executable. Such a location will be typically of the form:

$gidpathproblemtypes$CompassFEM_versioncompassfe m.gidexec

Note thattdyn.exe may be also executed from an arbitrary location if the directory path above is convinientlly added to the environment system variable PATH.

Finally, launch tdyn by using the following command line:

:> tdyn.exe -name “$inputpath$modelname”

Optionally, the argument -2D or -3D can be passed to tdyn.exe indicating the spatial dimension of the problem under analysis. In any case, Tdyn will check against the input file the validity of the specified dimension. If the given argument is not consistent with the input file information, Tdyn process will end with an error.

1.2.9.3. Output files generated during process execution

ProblemName.flavia.inf : Text file containing global information as well as process information for each time step. The content of this file can also be accessed during calculation through the GUI by using the menu option Calculate > View process info.

ProblemName.flavia.out : Text file containing detailed information of the calculation for each time step.

ProblemName.flavia.tim : Text file that contains a timetable giving information on the CPU time consumption of the process. The timetable contains a report of the execution time used by different parts of the problem. This file is only available after the successful calculation of a problem.

ProblemName.flavia.err : Text file containing error message (file created only if Tdyn exits with an error).

ProblemName.flavia.for : Text file that contains time evolution of the various components of forces and moments calculated over each body. This forces and moments file contains the forces and moments that act on the surfaces with Fluid Body properties assigned. Forces are often used to evaluate the convergence of a simulation. The file can be opened from within Custom GiD interface, using the options in the Utilities menu or in a spreadsheet program (like MS Excel) or another plotting utility (like Gnuplot). The first few time steps should be excluded from the graph, because the forces can oscillate at very high values due to the start up process, which can change the order of magnitude of the graph scales.

ProblemName.flavia.mov : Text file that contains time evolution data of body movements.

ProblemName.flavia.nor : Text file that contains time evolution information of the convergence norms associated to each problem variable.

ProblemName.flavia.res : Results file that contains all field valued results. When pressing Postprocess in Custom GiD, this file is loaded, and the results it contains can be visualized in the post-processing module. Also note that each calculation will delete a previous results file that might exist in this directory, unless it has been renamed before the new calculation process has been started.

ProblemName.flavia.rst : Restart file that contains the necessary results to be used when restarting a previous calculation. The restart file contains the velocities, pressures, and other relevant data of the last time-step that has been written into the restart file. If Tdyn is started with the option Restart: On (that have to be set in the PROBLEM window) the file ProblemName.flavia.rst is read and the calculation will be restarted using the last time-step data as initial condition. This file is updated each time-step that the results are written into the results file (ProblemName.flavia.res). Thus even a process that has not yet terminated can be killed and restarted with the option Restart: On, without having to recalculate all the time steps from the beginning. By killing the process, only the time steps from the last step that has been written into the results file onwards will be ‘lost’ and will have to be recalculated in case of a restart. Note that the restart file will be written in any case - even in the case that a calculation is started with the Restart: Off option. Also note that each time the restart file is updated, as well as with each new calculation, a restart file that might already exist in the problem directory will be deleted unless it has previously been renamed.

ProblemName.flavia.ram.res : Forces results for structural analysis using Ram-Series.

ProblemName.flavia.sat : Sink & Trim data.

ProblemName.flavia.ram.msh : Mesh for structural analysis using Ram-Series.