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[ICEM] Meshing Problem ?

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Old   November 13, 2014, 05:38
Default Meshing Problem ?
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Hello everyone,

I came across quite a weird problem.
I am simulating 2D flow around an airfoil with CFX. I am using the SST Gamma Theta Transition Model. The mesh is generated with ICEM.

My simulations reach convergence (1st attached picture) and everything seemed to be fine (velocity / pressure field / ... ) - then I took a look at the wall shear behaviour (2nd attached picture) - its is really jumpy which isnt right.

Now this might not sound like a meshing problem but I ve tried changing a lot of different parameters in CFX all with no success. Then I used a mesh a colleague of mine created with the exact same settings for CFX (considering turbulence model / settings / ... ) resulting in good results - thats why I am pretty sure this is a meshing problem.

I already did a mesh study on this (Yplus, streamwise grid refinement, cell expansion rate) but nothing solved the problem so I think there might be something wrong with the way I created my mesh.
Ive also attached the .rpl file of my mesh. (3rd attachment)

Hope anyone has ideas on this since Its really bugging me and I want to know whats wrong

If you need any additional information be sure to tell me !

Best Regards,

Leif
Attached Images
File Type: jpg residuals.jpg (45.1 KB, 23 views)
File Type: jpg wallshear1.jpg (37.9 KB, 22 views)
Attached Files
File Type: c NACArpl.c (28.8 KB, 7 views)
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Old   November 14, 2014, 17:06
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davide basso
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Hi,
running the script ICEM complains about a missing Nacapoints file

Can you attach it as well?
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Old   November 19, 2014, 08:36
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hi !

sorry about the late answer ... here is the NACA file ... you have to remove the .txt file ending though
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File Type: txt Nacapoints.txt (992 Bytes, 2 views)
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Old   December 4, 2014, 18:09
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davide basso
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Hi there,
first of all sorry for the horrible delay of this reply.

Loading the replay script I noticed at least two things:
- quality is below 0.3 for about 100 elements and this could be e a problem, especially because they are located at the nose and the trailing edge of the airfoil.
- the nacapoints define a profile with a sharp trailing edge (the pressure side and the suction side converge to a point) but in your geometry the trailing edge is truncated...why?


In your case I would rather go for a 2D C-shaped blocking approach as, for instance, in the pictures attached.
Once the premesh is good enough, you can generate the 2D mesh and then extrude it to obtain the 3D mesh ready to be exported straight away, without the hassle of extruding the geometry also.

Hope this helps
Attached Images
File Type: jpg blocks.jpg (23.8 KB, 9 views)
File Type: jpg 2Dmesh1.jpg (73.7 KB, 10 views)
File Type: jpg 2Dmesh2.jpg (47.7 KB, 8 views)
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