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Prism layer needed to resolve laminar boundary (lowRe)

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Old   April 7, 2012, 07:15
Default Prism layer needed to resolve laminar boundary (lowRe)
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M10
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Mio S
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Hello.

I'm trying to simulate an airfoil with Reynolds range 10**4 - 10**5.
For now, I'm using k-e to initially obtain a converged solution, and then switching to k-wSST for a better separation. Yaw range is 0-20deg.

If anyone has an experience in this type of analysis, I'd love to know the layer thickness and #s of prism layers one should be using to capture the laminar boundary layer/laminar bubble/turbulent re-attachment (I believe this will be hard). If there's any other tips and tricks for low Re modeling would be appreciated.

Thanks.
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Old   April 11, 2012, 07:02
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Hi
I think to simulate properly the low Reynolds ranges, you need to generate a fine surface mesh, otherwise it will be hard to converge.
Good luck
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Old   April 11, 2012, 14:30
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You'll want to have a prism layer to give a y+ < 1. You can use the tool linked below to give you an idea of the grid spacing needed to achieve this.

http://www.pointwise.com/yplus/
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Old   June 11, 2012, 09:44
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you should have at least 10 layer inside the viscous sublayer...best luck
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Old   June 15, 2012, 16:21
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For low angles of attack, I usually try to estimate the thickness of the boundary layer by calculating the boundary layer thickness of a flat plate. This gives at least an idea how thick your prism layers should be in total.
This doesn't work for high angles of attack when flow separation occurs. But in this case, you will most likely get crap from most turbulence models, so I think it doesn't matter anymore how thick your prism layers are in the separation zone.
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airfoil, k-omega sst, low re, transition model

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