Hex core mesh: Connectivity of tet mesh to hex core through pyramid
Default settings in gambit does not generate transitional pyramid layers while making a hex core mesh. While generating a hex core mesh in gambit the default settings in gambit will generate a mesh in which the outer faces of hex core mesh are not shared by the tet cells. In this the quad surface of the hex cells are copied and split into tri's. These faces are then used to generate tet cells.
If a user wants to have transition through pyramids then he needs to change the default setting mentioned below to 0.
Edit--->Default---->MESH----->CARTESIAN----> HEXCORE_QUAD_SURFACE_SPLIT 0
The default value is 1.
FLUENT also shows a grid check warning if the hex core mesh read is made using the default settings. This can be ignored as it does not affect the solution. With the above modifcation to default value, FLUENT does not show any warning.