[Horst]

Dear cfMesh users and developers,


i am currently meshing a inland waterway ship with the goal of representing y+<1 which leads to a first layer thickness in the area of 0.00005 m. I am going for ~15 layers and a thicknessRatio of 1.2. The size of the finished mesh is around 25 mio cells.
The ships geometrie is not overly complicated but still offers some concave two dimensional curvature on the bow and aft. In this area i create really bad shaped layer cells which make the simulations crash. On the less complex areas the mesh is perfectly fine.

I attached two pictures which show a slice before and after layer generation. It is visible that the cartesian cells are allready diagonally cut and include some bad shaped cells before layer generation. After layer generation, the mesh is completely crooked and some points are even pentrating the boundary.
I experimented with surfaceFeatureExtract -angle and found, that it gets slightly better for higher angles, but that only means that i get 50k badCells instead of 60k badCells.





Does anyone know a way to solve or workaround this problem?
Could this be solved with a better .stl representation?




I am grateful for every reply!
Georg

[lourencosm]

1-Visualize cells better in Paraview, choosing "crinkle" in the filter settings.
2-In snappyHexMesh/layers, use relativeSizes=False
3-In snappyHexMesh/layers, try nLayerIter > 1, up to 20, or more (you want too many layers)

Check this tips:
https://cfdmonkey.com/tips-and-trick...snappyhexmesh/
https://cfdmonkey.com/snappyhexmesh/

Else, try swiftBlock alone or combined with snappyHexMesh.

Good luck!

[CFD_with_Skill-Lync]

Few things you can do:
1. Use feature edge refinement
2. Turn relative sizing off, give layer thickness appropriately
3. Use "surfaceFeatureEdges -angle *insert angle here* " to divide your STL into sharp edges, so you can refine each feature appropriately.
> For your case it would seem 90 degrees would be a good choice.