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Using Surface Roughness to Approximate Dimple Surface

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Old   January 7, 2016, 11:21
Default Using Surface Roughness to Approximate Dimple Surface
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Lawrence
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If there a good way to approximate a dimpled surface like that of a golf ball using surface roughness of the model surface/wall?

Trying to avoid modeling the dimples and the complexity and CPU times to get some quick approximate answer.

My actual problem have a textured surface that seem larger than the typical "surface roughness", I am just curious as when do "surface roughness" no longer is "surface roughness", but geometry...

Thanks ahead... Points toward any publish doc would be appreciated.
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Old   January 8, 2016, 09:40
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Kaya Onur Dag
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There are people in the forum can give better answers but here is my contribution.

Quote:
If there a good way to approximate a dimpled surface like that of a golf ball using surface roughness of the model surface/wall?
Trying to avoid modeling the dimples and the complexity and CPU times to get some quick approximate answer.
You can use a wall model with a log law and aerodynamic roughness to get the mean shear of your rough surface. Then you neither need to define all the small boundaries on your wall nor require super small time steps to satisfy CFL conditions in your very fine mesh which you had to create to define boundaries on super small structures.

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My actual problem have a textured surface that seem larger than the typical "surface roughness", I am just curious as when do "surface roughness" no longer is "surface roughness", but geometry...
I think it depends on how much detail you want to capture from your wall, or how much information you actually need from your wall. As an extreme example, I know some meteorology guys consider offshore wind farms as roughness patches.

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Thanks ahead... Points toward any publish doc would be appreciated.
If I understood you correctly googling"wall modelling turbulence cfd" should work well
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