Good tutorials or refs for advanced meshing

[pwray]

Hello
I'm still a beginner with FEM, but I am trying to take harmonic analysis results from Elmer to use with bempp.
Currently I have just a planar mesh used with shell or smitc solver, with an internal body for the exciter area onto which I apply a body force, and I learnt 'just enough' about building meshes in gmsh to do that.

But moving to bempp will I think require that I build a 3D model with the 2D mesh and field values from Elmer applied to both sides of a thin 3D shape.

The types of questions I need to answer include:
* What is the best approach? Build a 3D mesh to begin, and just present Elmer with portions of it, or start with a simpler mesh and later extend it?
* My internal body has normals in the opposite direction to the remainder of the larger exterior body, but bempp requires all normals of a face to point in the same direction. Can I use gmsh to generate internal bodies with normals in the same direction, or can I simply use a set of elements as a body?
* How to re-use portions of a meshed geometry (not just the geometry but the exact element shapes too) in different parts of a larger 3D mesh?
* Can I extend the mesh of an already-meshed geometry into a larger geometry, retaining the original mesh?

Can anyone recommend some tutorials or references which deal with these more complex meshing operations?
I will be doing the meshing operations from Python rather than using the manual gui tools.

Paul

[kevinarden]

https://www.salome-platform.org/
The most powerful mesh generation tool. There is documentation, a forum, and tutorials on its web site. The geometry module is a full featured geometry modeling tool. You can build from points, lines, curves, faces, or use primitives. Move, copy, rotate, sweep, sweep along curves, etc.
The mesh model has numerous meshing algorithms. You can also manual create meshed without using geometry. You can copy, translate, extrude elements, an sweep along a curve. You can combine meshes into bigger meshes.
A universal file of a mesh is exported for input into Elmer. You can group elements, by selecting, our group on geometric bodies, to create named bodies and named boundaries in the Elmer mesh.
There is a basic tutorial in Chapter 9
https://www.nic.funet.fi/pub/sci/physic ... dElmer.pdf
The universal file can be opened in ElmerGUI, however there is more capability in using ElmerGrid.
You can type ElmerGrid in a command line to get a list of options. Including the file types supported. The most common command is
ElmerGrid 8 2 myunvfile.unv -autoclean
One feature is that it will create a mesh.name file which uses the groups to name the bodies and boundaries, which allows you to refer to them by name in the sif file.
ElmerGrid can also be used to generated meshes, and manipulate meshes.
https://www.nic.funet.fi/pub/sci/physic ... Manual.pdf

[pwray]

Thanks Kevin.
Ive used Salome for the geometry modelling (less complicated than FreeCad in some ways).
May have to look at the meshing.

Paul

[annier]

A good article that discusses about handling mortar boundary conditions using Elmer software.
Gustafsson, T., Råback, P., & Videman, J. (2023). Mortaring for linear elasticity using mixed and stabilized finite elements. Computer Methods in Applied Mechanics and Engineering, 404, 115796. https://doi.org/10.1016/j.cma.2022.115796
https://www.sciencedirect.com/science/a ... 2522007526