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turbineSiting tutorial: slip condition at top boundary gives unexpected result

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Old   June 6, 2014, 05:25
Default turbineSiting tutorial: slip condition at top boundary gives unexpected result
Marcus Letzel
Join Date: Sep 2012
Location: Aurich
Posts: 35
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Dear Foamers,

in the turbineSiting tutorial (OpenFOAM 2.2.2) the slip condition at the top boundary does not seem to work correctly. My understanding follows the definition of the slip boundary condition given in Table 5.4 of the OpenFOAM user guide: the slip condition at the top boundary patch should ensure that the velocity vector U has its normal component w kept at fixedValue zero everywhere within this patch.

I run two test cases. Case turbineSiting1 is the unmodified turbineSiting tutorial. The converged solution after 252 iterations is shown in the first image turbineSiting1.jpg. Contrary to my expectation the vertical velocity component w is not zero at the top boundary patch at z = 1500 m.

The problem is amplified in case turbineSiting2 where the domain height has been reduced from 1500 m to 1200 m. The converged solution after 82 iterations is shown in the second image turbineSiting2.jpg. The nonzero w pattern at the top boundary patch at z = 1200 m is now even stronger.

In both cases I expect w to be plain zero everywhere at the top boundary patch with the slip boundary condition.

My questions:
  1. Has anybody encountered the same problem before, or could somebody please confirm the reported behaviour?
  2. Given a positive response to 1., where and how does the source code need to be modified in order to fix this problem?
Looking forward to receive your feed-back.

Best regards,
Attached Images
File Type: jpg turbineSiting1.jpg (22.3 KB, 28 views)
File Type: jpg turbineSiting2.jpg (25.5 KB, 26 views)
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File Type: zip (18.3 KB, 4 views)
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slip, turbine siting

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