First to second order conversion

Netgen
1

Hi,

does Netgen have an option (possibly accessible by a preprocessor using Netgen plug-in for meshing) to mesh with linear tetrahedrons and then convert them to second order by just adding nodes in the middle of the element edges ? In Gmsh, this can be achieved using the SecondOrderLinear option. The idea is to avoid the mid-side nodes being snapped to the geometry since it may lead to negative Jacobians in some cases with complex (or messy) CAD models. I haven’t found such a feature in Netgen yet. I’ve even seen some preprocessors setting second_order to 0 only to convert the meshes to 2nd order themselves for the same reason.

2

Hi, just remove the geometry (SetGeometry(nullptr) )before calling second order curving, then this is what happens.

3

Thanks for the reply. And it’s possible when using Netgen through a 3rd party preprocessor, yes ? I’m asking on behalf of the FreeCAD community. We have an interface for Netgen (Conflicts between Netgen and FreeCAD's Fem module) and I’m trying to better understand how it works and improve it a bit.