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June 24, 2010, 10:22 |
LES of a square cylinder
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#1 |
Member
Join Date: May 2009
Posts: 54
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Hello,
I am having what I presume are inlet or grid quality issues with an LES case for a square cylinder. As can be seen in the attached images, the inflow to the left of the cylinder shows a strange behaviour with a variation of U (in attached image, coloured by U mag). My initial guess was that the aspect ratio or the grid quality overall is not good enough for LES. My grid does pass all checks inside of checkMesh. I am using the dynamic Smagorinsky model (simple filter and cubeRootVol delta) with a hex + polyhedra (due to local refinement) grid of ~1.6 million cells. The Re = 22,000 and y+ average = ~6 after approximately 20 non-dimensional flow-overs, which I presume could be an issue as well as I am using the nuSgsWallFunction on the cylinder wall patch. I will try to construct a y+=1 grid and avoid the use of wall functions next. My nuSgs file: Code:
dimensions [0 2 -1 0 0 0 0]; internalField uniform 0; boundaryField { inlet { type zeroGradient; } outlet { type zeroGradient; } sides { type cyclic; } cyl { // type zeroGradient; type nuSgsWallFunction; value uniform 1; } sym { type symmetryPlane; } } Code:
dimensions [0 1 -1 0 0 0 0]; internalField uniform (0.022 0 0); boundaryField { cyl { type fixedValue; value uniform (0 0 0); } inlet { type fixedValue; value uniform (0.022 0 0); } outlet { type zeroGradient; } sides { type cyclic; } sym { type symmetryPlane; } } -Grzegorz |
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June 24, 2010, 12:33 |
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#2 |
Senior Member
Daniel WEI (老魏)
Join Date: Mar 2009
Location: Beijing, China
Posts: 689
Blog Entries: 9
Rep Power: 21 |
Sorry, but I have to say your mesh looks bad, and is better not be called LES.
And what's more, it seems your inlet has a velocity profile, that's strange, isn't it? You can upload your case file in tgz format, so that we could have a look, we need 0/ constant/ system/
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~ Daniel WEI ------------- Boeing Research & Technology - China Beijing, China |
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cylinder, les, nusgs, square |
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