SideSetsFromNormalsGenerator produces speckled pattern instead of the full surface

[thiloschmid]

Dear all,

I'm a relatively new user of moose and for my first non-tutorial simulation I am stuck at defining sidesets in order to define boundary conditions. I have a mesh generated with gmsh that consists of a single surface. I wanted to use the SideSetsFromNormalsGenerator to simply have a separate sideset for the x and y side. If I only output the mesh the result is the speckled pattern seen below:

My code looks like this:

[Problem]
    solve = false
[]

[Mesh]
    [roi]
        type = FileMeshGenerator
        file = 'mesh.msh'
        dim = 3
    []

    [sideSet]
        type = SideSetsFromNormalsGenerator
        input = roi
        new_boundary = 'x-side
                        y-side'
        replace = true
        normals = 
            '1 0 0
             0 1 0'
        tolerance = 1e5
        variance = 1e-1
        fixed_normal = false
    []
[]

[Outputs]
    exodus = true
[]

The goal would be to have the whole side covered. I tried playing around with the tolerance and variance parameters but without improving the result. The files I used are

sideset-problem.zip

I also tried to use the SideSetsFromPointsGenerator but that did not produce any sideset at all.

Perhaps Moose is not the right tool for the job. However, e.g. Paraview does not offer a straight-forward way to define new sidesets or something similar. If you have an idea of any different approach or a different tool I could use, or if you think this is the wrong way to go proceed I would be happy to hear other suggestions.

Thanks a lot!

[aeslaughter]

Boundaries such as this are typically added with the program that created the mesh. I am not familiar with gmsh, but perhaps @lindsayad could help out.

[thiloschmid]

Thanks for your comment.

Yes, I figured that there must be some other possibilities. I'm currently working with a single .stl file that encodes the full surface. In gmsh there is the possibility to assign different physical groups to geometric entities but at least in the GUI I could not find the option to split my one surface into multiple geometric entities in order to assign different names to different sections.

[GiudGiud]

The tolerance you are using on the sideset generator is too big. I think you meant to use 1e-5 not 1e5

[thiloschmid]

Changing the tolerance parameter was one of the first things I tried. At least visually, the values 1e5, 1, 1e-5 and 1e-10 all produce the same result.

[GiudGiud]

Closing this.
I ll add a note to the sidesetfromnormalgenerator. It also does internal faces.
The right one to use here was
https://mooseframework.inl.gov/source/meshgenerators/SideSetsAroundSubdomainGenerator.html
with a normals argument