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ChrisPro December 3, 2011 12:52

Wing - internal flow

I'm trying to mesh a stl file of a wing.The wing is hollow and I want to simulate the internal flow, from one side of the wing to the other. So the inlet should more or less have the shape of an airfoil profile. The wing has some holes where the fluid can get through, so also the outside of the wing hast to be meshed.

At the inlet i only set the pressure. the velocity is calculated according to it.
But it is really important, that all of the flow gets throug the paraglider.
To mesh the file I use snappyHexMesh, of course.
But, now that I've tried several ways and didn't succeed, I need your help!

In the blockMeshDict file i made a block, where the stl file is in and touches one face of the block with its open side. To make a airfoil shaped inlet, I made another block, with splined edges and merged it to the first block.

But when i start snappyHexMesh I alsoways get the FATAL ERROR:
cell 15 (or any other number) of level 0 uses more than 8 points of equal or lower level

I also tried to give the face of the first block the shape of the airfoil and make this the inlet, but that doesn't work either.

Has anyone an idea, how I can fix this problem?


Antti May 10, 2012 10:10

Similar problem

Did you find a solution to your problem? Because I'm having a similar crash with sHM and can't find any info on what is causing it and how to stop it from happening. The only clue is that changing maxGlobalCells in castellatedMeshControls to a lower value seems to make the error go away. Trouble is that I'd need more detail for the mesh and so a larger number of cells.


ChrisPro May 10, 2012 13:29

Hey Antti!

Yes, If you want to mesh a stl-geometry from the inside, just make a mesh with blockMesh which covers the geometry and then set the "locationInMesh" to a point inside the geometry.

this is it :)


Antti May 11, 2012 04:49

Hi Christian,

Thanks for your reply. My case is different in that I actually want to mesh the outside of an object, but similar in that it produces this error you were having:


But when i start snappyHexMesh I alsoways get the FATAL ERROR:
cell 15 (or any other number) of level 0 uses more than 8 points of equal or lower level
I guess selecting the correct locationInMesh fixed it in your case? Maybe the reason is different for me. I can get it to build the mesh when global number of cells is set to 2M, I think this prevents sHM from doing the suface refinement which is apparently the part of sHM having this problem.

Thanks again for your reply.



ChrisPro May 11, 2012 14:35

...and you're sure you didn't set the locationInMesh variable to a value which is directly on the surface?
Try to set this variable to a completely different value. for instance a meter away from the geometry

Antti May 18, 2012 02:54

That was probably the reason, thanks! I'd set the locationInMesh too close to the surface.

But I'm still saying "probably" because snappyHexMesh still crashes, only now because it doesn't honor the maxGlobalCells limit and runs out of memory in the Shell Refinement phase. I'm going to try to find a solution for that now.

ChrisPro May 18, 2012 03:26

:) k

maybe you have a symmetry plane in your case, then you can simulate just half of the case. This would need much less memory!

If not you propably have to use a computer with more memory


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