[finzeo]

Hi all,

I am using OF v2106 to mesh an external flow case around a vehicle. The problem is somewhat minor, but I'm interested in correcting it.
It occurs during the snap stage. The cells that are located in the corners of the domain (cells with two or more faces in different patches) are "flattened", as seen in the images, which intuitively seems totally unnecessary. This in some cases generates some noise. This does not happen in the corners of the base mesh made with blockMesh (only in corners given by two .stl surfaces).

I tried varying the snapping parameters quite a bit. I see better results using explicit snapping. I tried using surfaceFeatureExtract and even "manually" generating the eMesh files (using Paraview and the "feature edges" filter). In addition to leaving images, I upload my dictionaries.

Thanks in advance.

[finzeo]

Any suggestions?

[AtoHM]

Depending on how you create the underlying blockMesh, the outer cell walls need to be shifted inside to snap to the geometry. Usually the blockMesh needs to be a bit larger than the geometry to work relyably. Which leads to my question: how do you create the blockMesh?
You might be able to move the initial blockMesh boundary very closely to the geometry, if you run with a high precision in controlDict. Then the shifting should be minimal.

[finzeo]

Originally Posted by AtoHM

Depending on how you create the underlying blockMesh, the outer cell walls need to be shifted inside to snap to the geometry. Usually the blockMesh needs to be a bit larger than the geometry to work relyably. Which leads to my question: how do you create the blockMesh?
You might be able to move the initial blockMesh boundary very closely to the geometry, if you run with a high precision in controlDict. Then the shifting should be minimal.

Thanks for your reply,


I tried several options: making the blockMesh mesh boundaries 1e-5 to 1e-8 larger than what is bounded by the .stl files. I attached my blockMesh, it really is a simple setup.
Similarly, something similar also happens on the corners of the interior .stl surfaces, that is, not only on the corners on the outer borders of the domain (associated with blockMesh).

[AtoHM]

Well ... I guess we got to see it.
Can you create just the blockMesh and show that corner and where the geometric surfaces are?

[finzeo]

Originally Posted by AtoHM

Well ... I guess we got to see it.
Can you create just the blockMesh and show that corner and where the geometric surfaces are?

Hi AtoHM,


Here is the case folder. Also, I attached as you requested an image of the base mesh made in blockMesh, with the corresponding surfaces, in the corner of interest. Don't pay attention to the addLayers stage, just run the first two stages to see the problem.


Just copy the stl file that I compressed separately (for size reasons) into constant/triSurface.