[thomas.]

Hello all,

I have been searching through the web for this simple questions with no success: how to create a not-trivial geometry, create the respective patches in order to do the meshing with snappyHexMesh. This, by using only open source software.

I created the geometry with Freecad and exported it in .ast (ASCII-.stl) format. I created the geometry from the basic primitives and then ran the fusion-boolean (attached picture).

As for the meshing, I have been trying following ways:

1. I tried to separate the surfaces into regions with surfaceAutoPatch. Then, create a .vtk-file with surfaceConvert to recognize the regions in Paraview. This may work, but I would like to find a more general way in order to apply it for every case, no matter how complex the geometry is.

2. I tried to export from Freecad single .ast files for every patch (inlet, wall, outlet etc.) with no success. When I click on the inlet and try to export it, it exports the whole part and not just the inlet. Same for outlet, walls etc.

3. Open the same Freecad file in Netgen. But here I don't know how to proceed to create the patches in order to be able to export a suitable mesh for snappyHexMesh.

4. I will try now the Blender+swiftBlock+swiftSnap alternative.

Generally speaking, I'm quite confused when it comes to the geometry/mesh creating procedure. I would REALLY appreciate any help.

Thanks in advance!

[vatavuk]

Hi Thomas,

Did you try to use snappyHexMesh?

I think that a good starting point to learn snappy, is to study it's use in the tutorial below:
https://www.hpc.ntnu.no/display/hpc/OpenFOAM+-+Spillway+Tutorial

Best regards,
Paulo

[thomas.]

Hi Paulo,

that's actually my goal! I don't have trouble with that part though (thanks for the tutorial anyway!). I somehow got stuck with the "trivial" part of the CAD/patch- creation part (exporting the .stl file and then beeing able to create/recognize the patches), but I already found a possible solutiont: just exporting the .stl (ASCII) file, then applying surfaceAutoPatch and then surfaceSplitByPatch. The patches created with surfaceAutoPatch can also be recognized with the Selection Display Inspector in Paraview.

Best regards,
Thomas

[vatavuk]

Hi Thomas,

I haven't tried, but i think it's possible to generate the mesh using snappy and then using the CreatePatch tool.

Best Regards,
Paulo

[thomas.]

Hi Paulo,

Thanks!