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-   -   Divide Prismatic Boundary Layer Mesh causes overlapping faces (http://www.cfd-online.com/Forums/engrid/136487-divide-prismatic-boundary-layer-mesh-causes-overlapping-faces.html)

SilentRunner42 May 29, 2014 09:46

Divide Prismatic Boundary Layer Mesh causes overlapping faces
 
Firstly. thanks for your support with Engrid. It’s a really useful free tool.
My problem is that when I try to divide the prismatic boundary layer Engrid says that there are overlapping faces. Specifically:
I have an STL file that contains a thin blade. I split this into separate files using Meshlab to provide separate upper and lower boundary codes (a test to re-combine them showed that it remained watertight with no overlapping faces).
I then imported it into Blender to provide a surrounding box in a similar manner to the tutorial. I then exported it to Engrid and applied the boundary codes etc. I then improved the surface mesh (one iteration) and exported the result to Meshlab to ensure watertight and no overlapping faces. I then created the prismatic boundary layer (1 iteration). This worked. I then tried to divide the layer but Engrid complained saying there were overlapping faces.
I exported all to an STL file and Meshlab showed that there were overlapping faces but only on the boundary layer mesh itself. The actual blade mesh directly below was smooth, quite flat with wide nicely generated triangles. I tried to fix this problem using “Fix Triangulation” in Engrid but it failed with “there appears to be a bug in Engrid”.
My questions are:
Is this a known bug in the prismatic layer tool?
Is there a way to remove/replace the overlapping faces in Engrid, or outside (then re-import it so that the boundary layer mesh is still recognized as such)? I tried exporting to Blender but I could not see the boundary layer mesh in the Blender view even though the file size had increased (suggesting it had been saved).
Any help would be brilliant. Thanks.

SilentRunner42 June 1, 2014 11:22

Solution - workaround
 
I found a possible way around this:
If the boundary layer meshing fails then create a volume mesh and repeat the division.
In my case the volume mesh worked (one iteration) - so I tripple saved it:). Then dividing failed after a long time but I think that is because I am using a 32 bit windows version which bombs out (like every other 32 bit app) when the memory usage exceeds about 1.2GB. Will try on a 64 bit pc and update.
If anyone has any other pointers, please shout :D.

eaglemckenna July 26, 2014 08:39

1 Attachment(s)
Hi
I am having the exact same problem - did you get around it?
I manage to create a prismatic boundary layer but receive an error of overlapping faces - when I am certain there are none on the geometry itself.


I can create a prismatic boundary layer, but when I try to divide the layer I once again receive the "there seems to be a bug in engrid" error, so once I attempt to improve volume mesh (netgen) I once again receive the overlapping faces error - I would be most grateful for some guidance (see attached - geometry with prismatic boundary layer)

kind regards
g

SilentRunner42 July 28, 2014 16:13

Did you try to create the volume directly after creating the prismatic boundary layer and before dividing it? Doing this worked for me.
Another way might be to use more iterations when creating the layer, save it to an stl file and import it into Meshlab to show any overlapping faces. This should then show whether the original mesh needs to be improved before you create the layer.

KateEisenhower May 4, 2015 03:37

Quote:

Originally Posted by SilentRunner42 (Post 503480)
Did you try to create the volume directly after creating the prismatic boundary layer and before dividing it? Doing this worked for me.
Another way might be to use more iterations when creating the layer, save it to an stl file and import it into Meshlab to show any overlapping faces. This should then show whether the original mesh needs to be improved before you create the layer.

Hello,

according to your previous posts you experienced overlapping faces after creating the boundary layer, but nethertheless you could create a volume mesh. Does this mean you are running your solver on a mesh with overlapping faces?

Best regards,

Kate


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