Definition of the mesh

    MATISSE, the post-processor used in this study will generate an unstructured mesh. This will be done step by step as it is described  in what follows.

1st step: Definition of the bathymetry

    The bathymetry is the coordinates (x,y and z even for using TELEMAC2D) of all the points in the calculations field. Instead of entering the coordinates of the all points, only the most important points were defined and the bathymetry was then interpolated by the software.

    The lines linking these points were created and the result was a first definition of the calculations field. Some points were defined as hard points to be sure that they will belong to the mesh. It is also possible to define "hard lines", which means lines belonging to the mesh. To do that, the lines defining the minor bed of the river were selected before generating the mesh. That ensured that these lines belong to the mesh, which is not obvious in unstructured meshes.

2nd step: Definition of the criterion

    Before generating the mesh, a criterion must be defined to let the mesh to be refined in the minor bed of the river. So the minor bed was selected and the criterion was chosen equal to 200. The plain was then considered and its criterion was 20. The global criterion was defined as the maximum of the two criterions.

3rd step: Generation of the mesh

    Before generating the mesh, MATISSE gives an estimation of the number of nodes. From this information, it is possible to estimate the CPU of the future caculations and the mesh can be changed if the calculation time seems too long. That is very convenient and prevents the user to run endless calculations. The mesh is then generated and the boundary conditions have to be defined.

The four "hard lines" defined previously belong to the mesh, as it can be checked in the following detail of the mesh: