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Old

Airfoil NACA 23012 results, transonic flow

Posted May 28, 2013 at 06:38 by skeptik (CFD notes)
What i've got about my airfoil (exp and Fluent data were extracted from article, but it's in russian. originally exp data from TZAGI report)
Click image for larger version Name: M06_rhocentral.jpg Views: 1369 Size: 87.8 KB ID: 143

So there present oscillations, they were caused by second order schemes. I'll simulate it on upwind later.

The differences in p fields are showed here:

upwind
Name: firstOrder.jpg Views: 5405 Size: 15.1 KB
linear corrected 1
Name: secondOrd.jpg Views: 3884 Size: 16.8 KB
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Old

2D-empty vs pseudo 2D upd. results

Posted April 18, 2013 at 03:53 by skeptik (CFD notes)
Updated April 18, 2013 at 04:15 by skeptik
Pseudo 2D results is here on the graph
Name: kOmega_PisoHexPseudo2D.jpg Views: 1923 Size: 39.2 KB

Cx is predicted very well, so let's make a comparation with 2D results

Name: table_en.jpg Views: 1587 Size: 31.4 KB

The difference is really big on supercritical angles, the PISO's results on 2D tetra meshes were also bad and quite similar to the 2D hexa's results.

So, it's better to use PISO with symmPlane or slip BC on domain's sides

#OpenFoam #2Dairfoil
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Old

2D-empty vs pseudo 2D - symmPlane

Posted April 15, 2013 at 05:35 by skeptik (CFD notes)
It seems there is big difference in case with 1-cell thick domain where we set empty BC compare to case with 5-cells or 3 - cells thick where we set symmPlane

for SST and NACA23012 we have (17 and 15 grad angle of attack)

Click image for larger version Name: table.png Views: 792 Size: 14.5 KB ID: 137

So when we use PISO, it would be better to use 5 or 3 -cells thick domain.
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Old

blockMesh,snappyMesh and experimental results for 2D airfoil

Posted April 1, 2013 at 05:17 by skeptik (CFD notes)
A certain Mahdi wrote me via e-mail, that my tetra-mesh and hybrid mesh was not good for simulations.

So here i show results which were obtained with C-mesh generated by blockMesh utility OF, and snappyHexMesh.

blockMesh domain

Name: hexaMesh1.jpg Views: 12142 Size: 76.8 KB

mesh near wall

Name: hexaMesh2.jpg Views: 9227 Size: 88.2 KB

snappyHexMesh domain

Name: snappy1.jpg Views: 6706 Size: 86.3 KB

boundary layer discretization

Name: snappy3.jpg Views: 10793 Size: 85.5 KB
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File Type: jpg hexasSimple.jpg (44.1 KB, 4824 views)
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Old

about polyDualMesh "Try something smaller than 90"

Posted March 28, 2013 at 02:06 by skeptik (CFD notes)
Quote:
Originally Posted by lillberg View Post
Try something smaller than 90 deg feature angle since it represents the maximum angle between two neighboring surface normals on a surface without corners. That is, the mesh will consider your surface shape a corner if the angel is larger than this value. I typically use something between 45 and 80 depending on the tet mesh resolution on highly curved surfaces. This might be the root of your problem. Looking at my picture the curved surface in the middle would (wrongly) be treated as a corner if
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