Hexahedron 27 nodes
 

Hello,

I have a test.geom file to generate a structured hexahedron mesh.
If I run gmsh with this option -order 1 I get what I expect that is to say
hexadrons with 8 nodes.
When I use the option -order 2 I get hexahedrons with 20 nodes.
How can I get hexahedrons with 27 nodes ?
Thanks a lot

You specify second-order, you get second-order. However, these would only be useful for a FEM and not a control volume code.

In case you didn't notice the gmsh manpage, it describes where all these nodes are located:
http://www.manpagez.com/info/gmsh/gm....0/gmsh_60.php

Or just google for second-order hexahedron (that's how I found the above manpage), I'm sure you will find something useful there. If not, you'll have to switch to a FEM forum where the people would know something about these types of shape functions.