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SnappyHexMesh bad snapping for 2D airfoil

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Old   October 6, 2013, 04:56
Default SnappyHexMesh bad snapping for 2D airfoil
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Dear CFD-online users,

I have a problem with snappyHexMesh. The castellating all works fine, but when it comes to snapping the cells at the boundary look really strange. I have tried a lot now, but it seems I am overlooking something.

Since it is 2D, I first only castellate the mesh and then extrude it. Subsequently, I snap it and add layers. The RunMesh.sh does all that.

Could you have a look at the case files and tell me what I am doing wrong, because I do not see it anymore?
Link to case files: https://www.dropbox.com/sh/lyi8po231fxnb2k/96Crfo7v_s


Thanks a lot!

P.s. If anyone knows how to easily convert an 2D airfoil with x,y coordinates to an stl file needed for SHM, it would be very much appreciated if you could also tell me that!
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Old   October 6, 2013, 16:58
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Dear Maero,

Did you check out the dictionary in the plunging wing tutorial?

You don't need 16 cells between layers. It only makes your mesh bigger. Remember, snappy always refines the mesh in 3D.
Increase nSmoothPatch to lets say 6 and then see where that gets you. Increase nRelaxIter to 100.
And remember, snappy runs fine in parallel.
Let me know what happens.

- miro
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Old   October 12, 2013, 06:20
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Thank you Miro! I knew it had to be some minor adjustment.
It worked like a charm. The 2D case now runs good. I still have to try 3D but that shouldn't be a problem I guess.

Thanks!
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Old   October 14, 2013, 11:43
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Hey,

I still have another question about SHM. When I want to refine the region around the airfoil, I use:
airfoil
{
level (6 9);
}

But if I increase the 9 to 11 for instance to refine around the airfoil, then it takes SHM very long to solve for the mesh (it already takes 10 minutes for (6 9) with 8 processors), because the non-extruded mesh contains more than 10 million cells.

So my question is: Is there any way to refine the mesh around the airfoil without having to extrude a mesh of more than 10 million cells?

Also when I increase the refinement, no layers will be added anymore.

Thanks!

Last edited by maero21; October 14, 2013 at 12:56.
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Old   October 18, 2013, 14:18
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Quote:
So my question is: Is there any way to refine the mesh around the airfoil without having to extrude a mesh of more than 10 million cells?
I'm not sure what you wanted to say here, but number of cells grows pretty fast.
I'm not sure that no boundary layer is a good idea.
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