Dear friends:

Would you please give me some information about where to download a free code to generate unstructed grid, both the Tet and Hex. the code can export the grid to a text file. regards

Hello,

We have developed an unstructured mesh generator for tetrahedral grids with prismatic boundary layers; it can be found here: http://www.engits.com/cms/index.php?id=16. As input you need a surface triangulation that you can create, for example, with NETGEN or Gmsh. You can export the mesh in the ASCII Gmsh format which can be easily understood. We will soon publish a new version (current version is 0.9) which includes direct export to the OpenFOAM format. The tetrahedral part of the grid can then, optionally, be converted into polyhedral cells.

If you want a purely hexahedral grid generator the snappyHexMesh tool from OpenFOAM might be your choice. Have a look on the OpenFOAM website: http://www.opencfd.co.uk/openfoam/

Both tools are licensed under the GPL.

Regards,
Oliver

can it work for 2d problem and how to define the bc

Both tools are really for 3D problems. For 2D have a look at Gmsh: http://www.geuz.org/gmsh