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# Postprocess

#### How can GiD read postprocess information?

GiD reads several files with postprocess info in a GiD-defined format. As the information is really in a very easy format, your code (or one interface program), should write the results of your analysis in GiD postprocessing format. It is very easy to do it. Some people have modified their code for GiD in 2-3 hours. The GiD postprocessing format is defined in the reference manual and in the interactive help.

Some result format are also imported in postprocess:

- FEMAP
- TECPLOT

#### Can GiD display results on Gauss points?

With version 6 or newer it is possible to visualize results in Gauss points, both in automatically calculated and introduced by the user.

Gauss points are several points inside every element, that are used to perform the integration quadrature necessary for the FEM. For this reason, the main variable of the problem is obtained in the nodes and the variables that need an integration of this, are obtained in these Gauss Points.

Current version can already read and display data in the Gauss points. The standard possibilities are:

- Linear (beam) elements: any number of points inside, equally distributed.
- Triangle: 1,3,6 GP in standard positions.
- Quadrilaterals: 1,4,9 GP in standard positions.
- Tetrahedra: 1,4,10 GP
- Hexahedra: 1,8,27 GP

Note: Standard positions means the positions of the quadrature of Gauss-Legendre. If your positions of the points is different, it is also possible to introduce user-defined positions.

Gauss points positions for triangles and quadrilaterals.

One Smoothing algorithm is the one that, given one variable defined on Gauss Points, calculates the value of this variable in every node of the mesh. The easiest way to do this is, for every element, transport with the shape functions the values to the nodes, and do the mean or one weighted mean of the several values calculated for every node.

#### For higher degree elements, can results be visualized in the additional nodes?

Current version can read higher degree elements but will display them equal than if they were its simple version. For example, displaying 6-noded triangles is the same than displaying 3-noded triangles.

#### I read the postprocess mesh with mesh read. Is it correct?

Instead of using "meshread", you shoud probably input inside the postprocessor two files:

- For the mesh, use: test.flavia.msh (old formats as test.flavia.bon or test.flavia.dat are unrecommended)
- For the results use: test.flavia.res

Check the manual for the sintaxis format.

If the mesh is already in the preprocess, it is necessary only the results file. It must have the name MODEL.flavia.res and be inside the directory MODEL.gid In this case, when going to posprocess this file is automatically read.

#### In the postprocessing .res files, what happens with headers?

The name of the result must be 15 characters long. If it is shorter, the remaining space until 15 can be blanks.

#### Could you provide me with a simple procedure to visualise a 3D velocity field with streamlines?

The easiest way to define a stream line in a 3D mesh is to select a point by giving its coordinates. The stream line that goes through this point is drawn. In the contextual menu there are other ways to select several points at once. Tipically, a cut is made in the middle of the volume mesh and the points are selected in the cut.

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