# Boundary layer thickness

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 June 16, 2010, 12:38 Boundary layer thickness #1 New Member   Tomasz Merda Join Date: Jun 2010 Posts: 4 Rep Power: 9 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?

 June 17, 2010, 04:15 #2 Member   Join Date: Jun 2010 Posts: 33 Rep Power: 9 Can you post the equations that you have used thus far? So we know which ones you have and have not tried? Cheers, T

 June 17, 2010, 08:21 #3 New Member   Tomasz Merda Join Date: Jun 2010 Posts: 4 Rep Power: 9 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)

 June 21, 2010, 15:35 References #4 New Member   deja pong Join Date: Jun 2010 Posts: 1 Rep Power: 0 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

 June 22, 2010, 07:58 #5 New Member   Tomasz Merda Join Date: Jun 2010 Posts: 4 Rep Power: 9 Thanks Now I must translate this

 June 22, 2010, 08:51 #6 Senior Member   Join Date: Nov 2009 Posts: 411 Rep Power: 13 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 !!! Do

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