The tab "General settings" contains three blocks:

Discharge calculation at offtakes

This block rules the criteria of the iterative calculation at offtakes. The parameters are the maximum number of iterations and the precision to reach in m³/s. The default values are suitable for most cases. It could be necessary to refine theses criteria if one ask a greater precision inthe precision at nodes in steady calculation parameters or in the precision of the non linear system in unsteady calculation.

Ce bloc règle les critères du calcul itératif aux prises. Les paramètres sont le nombre maximum d’itération et la précision à atteindre en m³/s. Leur valeur par défaut convient pour la plupart des cas. Il peut être nécessaire d’affiner ces critères si on demande un précision importante dans la précision aux noeuds en calcul permanent ou dans la précision du système non linéaire en calcul transitoire.

Automatic head loss at expansions

An automatic head loss at expansions may be added to take into account the loss of hydraulic head at locations where the cross section is getting suddenly larger (width increasing and/or bed elevation decreasing). In this case, a head loss is added using the Borda formula $\Delta H = c (V_{upstream} - V_{downstream})^2 / 2g$ where ${c}$ is a parameter dependent on the angle ${\alpha}$ of the enlargement:

• $c = 0.525 ln(tan(\alpha)) + 1$ (Neperian logarithm)
• $c = 0$ for $tan(\alpha) < 0.15$
• $c = 1$ for $tan(\alpha) \geq 1$

Writing simulation results

There are two options:

• into the XML file project
• into a separated binary file

This option, when selected, is valid for the current scenario and all its variants. But you can change this option at any time, and thus have, if desired, disparate results in the format that you want for the various calculations, either for a scenario or for one of its variants, whether for a steady flow or an unsteady flow calculation. In the case of choosing the XML file, all the results of calculations performed for this branch of the project (scenario and variants) after this choice will be written in the XML project file. The advantage is to have all the input and output data in a single file. But the downside is that the XML file can become very large, and depending on the power of the computer (memory in particular), it can sometimes cause problems with losses of pieces of the XML file. We have indeed noticed that when the XML file is over 60 or 70 MB (megabytes), these problems can appear. In addition to the risks related to the size of the XML file, the time of writing and reading the results of this XML file can become very long. It is for these reasons that we have added the option of writing the results on binary files. These files have the extension .res for the results in steady or unsteady flow, and .rci for the initial conditions. The filenames with the .res and .rci extensions are constructed from the name of the XML file with an additional _ns_nv, where ns is the number of the scenario and nv the number of the variant (or 0 if it is not a variant, but directly a scenario). All these files are written into the subdirectory where the XML file is located.

How to write the XML file results

There are two options:

• Mono-thread
• Bi-thread

The bi-thread option on computers with multiple cores, significantly increase the speed of writing the results of the XML file in a simulation with Fluvia or Sirene. It has the disadvantage of not being completely stable and, in rare cases, crashes the simulation program at the time of writing the results.

Note on possible instabilities of the software

If you experience random crashes of Fluvia or Sirene calculation programs at the time of writing the results, choose the mono-threaded option.

If you notice any problem with the instability of the software and possible data loss, or even a complete loss of the XML file, then use the option with the results on binary files. Automatic backup .bak files are also created in the subdirectory of the project, which generally allows to recover the old XML file. It may also be safer to work directly on a subdirectory with automatic archiving (eg Dropbox), which will allow to retrieve all the intermediate versions of the files in case of problems.