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Vorticity unexpected results on airfoils

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Old   May 5, 2021, 06:31
Default Vorticity unexpected results on airfoils
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Hi everyone,


looking at various CFD simulations about airfoils, I have found unexpected visualizations about vorticity, especially on leading edge.

I send you here the configuration file and some screenshots about an example (NACA23012, Mach 0.15, Re6e6, AOA 4 deg).

The issue presents both with fully turbulent simulations and using BC transition model.


I expect to find smoother variation vorticity on leading edge to "link" the positive and negative values of vorticity on upper and lower surfaces.
I tried to change CFL and to increase the minimum number of iterations for the RANS, but the results doesn't change a lot.
On more complex geometries like multi-element airfoils, reducing the CFL seems to help reducing this unexpected result about vorticity, but the issue presents anyway.


May it happens due to 2nd order numerical method? I usually adopt Roe+MUSCL or JST.


I would like to understand if I my configuration file is missing something, or understanding if I am ignoring some theoretical aspects, then my judgement about is wrong.


Thanks in advance for any kind response.
Stefano
Attached Images
File Type: jpg Zoom_Grid.jpg (100.9 KB, 11 views)
File Type: png ZoomLE_Mach.png (98.4 KB, 9 views)
File Type: png Zoom_Vorticity.png (90.7 KB, 9 views)
File Type: png Result_Mach.png (90.2 KB, 9 views)
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File Type: doc template_cfd.doc (35.5 KB, 0 views)
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Old   May 8, 2021, 18:26
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I do not know this particular case, but if this location is close to the stagnation point, then you might have some local phenomena (separation bubble, skin friction peak) that might cause some numerical issues. It might be that locally, you need a finer mesh. It might be something else (turbulence model, numerics,..).



It would be good to compare with some measurements to see how bad this problem is. This will then also give you an idea about what kind of physics is going on near this point of concern.
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Old   May 11, 2021, 04:09
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Thanks for your answer.


I will try some modification to the grid or to the configuration file, trying to detect what is the issue.


Thanks again for your time.
Stefano
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airfoil 2d, su2 7.1.0, vorticity gradient in 2d

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