FreeCad FEM mesh: boundary, region and group. Which one and when?
Posted: 14 Apr 2024, 23:45
I am trying to use FreeCad to differentiate the Body and boundary elements on a mesh ( A PCB I design)
I use KiCad to export the PCB.
I use FreeCad to create the mesh, then the GMSH groups/faces
And then I import them to ElmerGUI.
I try to understand how to handle Body and boundary properties. If the mesh is simple/doesnt have a lot of edges/solid components its easier to select the faces/solids. Now I try to use a more complex mesh and when I manage to differentiate the solids shown in Elmer, my boundaries go "bad" and vise versa. I have questions in order to generate my mesh more professionally and correctly:
-in FreeCad there are FEM mesh boundary, region and group options and in each of them I can select either Face or Solid parts of my mesh. Which one creates the body and which the boundary for Elmer?
-Say I make a FEM mesh group. When and should(?) I put both a solid and face(s) in the same group?
-Can the GMSH element size negatively affect the body/boundaries set? (aka can there be a bug if the element size of the mesh is too big, and two bodies unite for example?)
(image link: https://i.sstatic.net/jtEPKG4F.png)
For now I try to use only FEM mesh group, as it looks like it can generate both body and boundaries for elmer. I do some trial and error for now, I think Im getting there, but I am unable to find a proper tutorial for elmer+KiCad about this specific topic, for -more-complex meshes.
I attach the step, the FreeCad project and the .unv export if someone needs to take a look at the shape/play around with it or show me something. I try to make the antenna and GND place as one body, and the FR4 as a second body. At the same time I need boundary for antenna signal input and boundary for the GND/bottom layer.
I use KiCad to export the PCB.
I use FreeCad to create the mesh, then the GMSH groups/faces
And then I import them to ElmerGUI.
I try to understand how to handle Body and boundary properties. If the mesh is simple/doesnt have a lot of edges/solid components its easier to select the faces/solids. Now I try to use a more complex mesh and when I manage to differentiate the solids shown in Elmer, my boundaries go "bad" and vise versa. I have questions in order to generate my mesh more professionally and correctly:
-in FreeCad there are FEM mesh boundary, region and group options and in each of them I can select either Face or Solid parts of my mesh. Which one creates the body and which the boundary for Elmer?
-Say I make a FEM mesh group. When and should(?) I put both a solid and face(s) in the same group?
-Can the GMSH element size negatively affect the body/boundaries set? (aka can there be a bug if the element size of the mesh is too big, and two bodies unite for example?)
(image link: https://i.sstatic.net/jtEPKG4F.png)
For now I try to use only FEM mesh group, as it looks like it can generate both body and boundaries for elmer. I do some trial and error for now, I think Im getting there, but I am unable to find a proper tutorial for elmer+KiCad about this specific topic, for -more-complex meshes.
I attach the step, the FreeCad project and the .unv export if someone needs to take a look at the shape/play around with it or show me something. I try to make the antenna and GND place as one body, and the FR4 as a second body. At the same time I need boundary for antenna signal input and boundary for the GND/bottom layer.