Couldn't get snappy to generate a mesh
Hello,
I try to generate a mesh for a geometry of a wind tunnel, given by STL files. It works finde with the Spider mesher and I try to adapt it to snappyHexMesh. The windTunnel file contains multiple solids. It works when using the configuration below. snap and addLayers are set to false. When I set snap to true, snappy still runs. But the mesh contains only the patch from bodySmooth and is reduced to one rectangular cell reflecting none of geometry. Thanks for any help and I would be happy to provide any more information! Florian Code:
/*--------------------------------*- C++ -*----------------------------------*\ |
Hey Florian,
I'm not sure if it is still the case, but earlier with sHM the different steps of meshing were stored in different time-steps. So if you go to the next time step in paraview you should see the snapping part you are missing to suppress this way of mesh generation type Code:
snappyHexMesh -overwrite Code:
snappyHexMesh Colin |
I use a little script that clears the polyMesh directory (except blockMeshDict), runs blockMesh and snappyHexMesh to ensure a clean start each run.
Of course I was locking at the final timestemp directory. |
Hey
could you give us a screenshot of the output what sHM delivers you? regards |
This is a screenshot with snapping disabled: http://xgm.de/upload/noSnap.png
and snapping enabled: http://xgm.de/upload/snap.png The output of blockMesh and snappyHexMesh with snapping enabled can be found at http://pastebin.com/ixMhTPrx thx! |
Next try:
is the point locationInMesh (3 0 0 ) in the part of the geometry you want to keep or not? This point has to be within the area you want to have meshed and here sHM seems to complain somehow: Code:
(0 seconds you only need for nothing). Another question that came to my mind is how is the scaling of the blockMesh and the .stl file(s), are they of the same unit (m, cm or mm)? |
Hello,
I'm pretty sure that (3 0 0) is in the mesh. It works fine using the same point with another mesher. I also tried a number of other points with no success. Regarding the scaling of the files. I have loaded the generated blockMesh and the STL files into paraview. They are of similiar size and the STL solids fit in the blockMesh completely. Why is it working without snapping if either the point or the scaling were wrong? Thx! |
Ok, I have removed the bodySmooth part entirely for now and it seems to work now (generating something that resembled the input geometry, by no way a perfect mesh).
I still got no idea what caused the problem, and why it happens only with snap enabled. Thanks for your help! |
Sry that I couldn't help you more specific.
Quote:
In the first place the problem looked much more trivial than it actually seems to be. regards |
Thanks for your help!
One more question: Is there a variable that globally controls the fineness of the mesh? In my other mesher I have a base cell size and all levels of refinement are based on this value. So if the mesh is good and I just want some more cells I decrease that base cell size. Is maxGlobalCells or maxLocalCells something like that? |
I think your sHMDict is missing something in the refinementSurfaces part…
I would rather use something like this: Code:
geometry Quote:
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Quote:
Let's say you have a 10m long domain with 10 cells. That means every cell will be 10/10=1m long. That is level 0. Level 1 will be 0.5m long, level 2 0.25m and so on. If you chose to have 20 cell, then your level 0 will be 0.5m, your level 1 0.25 and so on so the number of cells will increase. Usually this is not the way of working though, as you are probably aiming at increasing the mesh close to the body only and not everywhere on your domain. |
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