Tetmesh scheme questions & Gambit neutral fiel

I have two questions regarding meshing.

I am using the specific meshing schemes (tetmesh) and I want to know what “min tet layers” and “max growth rate” means.

Also, I am exporting a gambit neutral file and I am getting the coordinates of nodes and the nodes for each element. I also want to know the nodes that are on a specific surface and write them in the neutral file. Is it possible to do that?

Best Regards,

The “min tet layers” and “max growth rate” are parameters to the third-party triangle/tet meshing algorithms that we use.

Consider a trivial example with thin walls.

bri x 10
brick x 9
vol 2 move z 3
subtract vol 2 from 1
modify curve 27 33 32 30 35 26 28 31 blend radius 1
volume 1 size .7
#vol 1 scheme tetmesh
volume 1 scheme tetmesh proximity layers on 3
volume 1 tetmesh growth_factor 1.2
mesh volume 1

If I don’t specify the “min tet layers”, I get the best attempt at honoring the mesh size?

If I specify the “Min Tet Layers”, the algorithm detects thin wall and increases the mesh density in those areas. The actual number is used more as a hint than a guaranteed number of elements through the thin wall.

The “Max Tet Growth Rate” affects how quickly the tetrahedra grow from the small size to the requested size in the volume or to the default size if you did not specify a size on the volume.

I will not claim to be a Gambit expert. You can create a nodeset in Cubit that would translate to a Boundary Condition in Gambit. In Coreform Cubit you would do something like

nodeset 1 surface 2

In the Gambit neutral file that will produce a boundary condition card with the name “NS 1” where the “1” corresponds to the nodeset id created in Coreform Cubit.