[Gmsh] Help with output mesh conversion as tochnog input and conversion of tochnog output for gmsh postprocessing

Fernando Lorenzo felorenzo at att.net
Wed Nov 19 03:23:13 CET 2014

Dear fellow users,

My name is Fernando Lorenzo and I am one of the maintainers of the Tochnog Finite Element analysis application (tochnog.sourceforge.net). As some of you may or may not know, Tochnog is, just like Gmesh, an open source, very powerful and capable solver that can solve many different problem, like 
Differential equations (materials)
Convection-diffusion equation:

- Temperature calculations.


- Stokes and Navier-Stokes.


- Elasticity (isotropy and transverse isotropy).

- Elasto-Plasticity (Von-Mises, Mohr-Coulomb, Gurson, etc.; plasticity surfaces can be arbitrarily combined).

- Hypo-Plasticity (Von-Wolfersdorf, cohesion, intergranular strains, pressure dependent initial void ratio). 

- Damage.

- Thermal stresses.

- Hypoelasticity.

- Viscoelasticity.

- Viscoplasticity.

- Viscosity.

Ground water flow equation:

- Storage equation.

Wave equation.

Accuracy information
Residues in equations can be printed/plotted.

Error estimates for all data (stresses, forces, temperatures, etc.)

Interaction analysis
Automatic fluid-solid interaction.

Temperature effects on fluids, solids.

Contact analysis
Contact with and without friction.

Frictional heat generation.

Frames of description
Lagrangian, Eulerian, and AEL (arbitrary Eulerian Lagrangian) calculations.

Tochnog does not do magnetism and the most developed pre and post processing interface is for GiD, which, as you may already know is not free or open source. Tochnog meshing capabilities are limited for preparing complex meshes.

Gmsh appears to be the logical choice as it allows for geometry definitions, mesh preparation and assists with boundary condition setting, and can do some serious post-processing.

The idea to use Gmsh as pre and post-processor for Tochnog  is not knew but no updating has taken place. We have a couple of AWK scripts to do the conversion (see attached files) that can do the conversions but are not complete. The AWK scripts were developed some years ago by Osman Buyukisik and will still ned some updating as GMSH has also been updated.

I will be extremely thankful if some of you with better knowledge of handling text files can assist in the updating and conversion of the files to C or C++ so that they can be built into gmsh and offer the tochnog as an option for input  file preparation and to read Tochnog output to use gmsh as postrpocessor.

In addition to helping me keep Tochnog alive, I feel that it will expand GMSH capabilities as a source for solvers other than GetDP. 

My contributions to Tochnog have involved updating the application, building binaries, adding the ability to use the LAPACK solver, correcting some code and helping to maintain the application. However, I believe that some of you can probably convert the attached awk scripts and help me to either build those capabilities into GMSH, or allow us Tochnog users to have an external tool that allows full use of GMSH as a free and open source pre and post processor for Tochnog.

Your help and assistance will be greatly appreciated.

Fernando Lorenzo
felorenzo at att.net

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