snappyHexMesh - Refinement Level
I'm using OF 1.6.x.
I would like to obtain a car into tunnel mesh with 3 different refinement boxes (refinement mode inside).
See the attached picture.
First, I tried:
level 1 for "refinementBox_1", level 2 for "refinementBox_2", level 3 for "refinementBox_3", level min 4 max 5 for car surface.
I obtain the mesh but, for my case, it's not very thick.
Second, I tried:
level 3 for "refinementBox_1", level 4 for "refinementBox_2", level 5 for "refinementBox_3", level min 6 max 7 for car surface.
I obtain the mesh but I lost the refinement boxes! I have a thick mesh only around the car surface, but not into the 3 refinement boxes!
So, what am I wronging? Is there a bug in 1.6.x?
Is there a maximum global level for refine mesh?
Can it depend from the cells dimension in blockMesh?
How can I obtain my desired mesh?
Thanks for any reply
I'm not an expert at all, but t first reading, this comes to my mind:
If I were you, I would set up the surrounding mesh using blockMesh manually and then using snappy to add your special geometry.
thank you very much for you reply!
I have a car surface in .stl file (average tria dimension 6 mm).
The tunnel is in X 55 m, in Y 13 m, in Z 10 m. My car is in X 4.8 m, in Y 2 m, in Z 1.5 m. The cell dimension of blockMesh is 350 mm. So:
refinementBox1 -> level 1 -> 1/2 -> cell dimension = 175 mm
refinementBox2 -> level 2 -> 1/4 -> cell dimension = 87.5 mm
refinementBox3 -> level 3 -> 1/8 -> cell dimension = 43.75 mm
refinementSurfaces level (4 5)
This mesh is whit 3 boxes but is not thick.
If I try with
refinementBox1 -> level 2
refinementBox2 -> level 3
refinementBox3 -> level 4
refinementSurfaces level (5 6)
I lost my 3 boxes!!!
Do you think I have to refine my blockMesh?
I have to repeat, that I'm not experienced at all!
I just think, that the refinement areas and levels refer to the STL surface and intersections with it. As your boxes are far from the STL surface, they wont be refined. You give the level, alright, but for snappy there's no reason to refine as there's no related surface. That's how I understood snappy. However I'm curious why the first attempt seems to work.
On the other hand I remember somebody mentioning wake areas to be refined with refinement boxes (which would be an antithesis to what I wrote).
Anyway: To me it would be an easy workaround (or maybe just to give it a try), to mesh your boxes manually with blockMesh, i.e. meshing the boxes as described in the damBreak tutorial, each of them with a different grading.
P.S.: If you like... give your first version a try with refinementSurfaces level (5 6) and your second version a try with refinementSurfaces level (5 5), leaving the other settings as they are. I'm just curious what would happen...
what you describe in your first email is really strange...
It would be useful if you could post here your snappyHexMeshDict and maybe try with a more recent 1.6.x version.
I tried the first Wolle's advice: level 1,2,3 for the boxes and level (5 6) for the car surface: I got 3 boxes! Now I would like to increase the refinement level.
Before this test I tried whit OF 1.6 but whit same result...
This is my snappy dictionary:
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