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Old   June 16, 2010, 12:38
Default Boundary layer thickness
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Tomasz Merda
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Hi. I try to find a formula for boundary layer thickness for Re numbers 10e7 and higher. All formulas I find are for lower Re noumbers. Can anybody help me?
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Old   June 17, 2010, 04:15
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Can you post the equations that you have used thus far? So we know which ones you have and have not tried?

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Old   June 17, 2010, 08:21
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i only use Y+ parameter in Fluent. In Gambit I set BL thickness "on eye". I find some equations but for Re 10e5-10e6. I have Re 10e7-10e8.
equation is delta=0,37*l/sqrt5(Re)
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Old   June 21, 2010, 15:35
Default References
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deja pong
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Here is a reference that might be useful

http://www.desktop.aero/appliedaero/...yertheory.html

Specifically:

http://www.desktop.aero/appliedaero/blayers/lambl.html

With an interactive applet where you can adjust the Reynolds Number:

http://www.desktop.aero/appliedaero/...blsummary.html
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Old   June 22, 2010, 07:58
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Tomasz Merda
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Thanks
Now I must translate this
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Old   June 22, 2010, 08:51
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I think you both make a confusion between the Boundary Layer (which is a physical model, specifically a simplification of the the Navier Stokes equations) and Gambit's boundary layer which is a geometrical entity.

What you probably need is an estimation for the height of the first row of cells at the wall in your mesh (the starting dimension in Gambit's boundary layer), you can estimate this for any Reynolds number using this calculator:

http://geolab.larc.nasa.gov/APPS/YPlus/

It is unfortunate that Gambit uses the notion of boundary layer for a geometrical entity, but this has nothing to do with the Boundary Layer equation or theory !!!

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