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February 24, 2012, 15:45 |
Wall Roughness
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#1 |
New Member
Paul
Join Date: Feb 2012
Location: CT
Posts: 6
Rep Power: 14 |
I am trying to get a better understanding of what the "Wall Roughness" box is (in the wall boundary layer box) referring to.
Roughness Height: Is this the height found on standard charts? (see http://www.engineeringtoolbox.com/su...cts-d_209.html). i.e. If I was to use Stainless Steel than the Roughness Height would be k=5E-5ft. Roughness Constant: Is the roughness constant the number calculated (relative roughness). i.e. Using the hydraulic diameter (d=23.5in), and k. Equation is r=k/d == having a value of 26E-6. Can someone please help? Thank you! Paul |
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February 24, 2012, 15:57 |
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#2 |
Senior Member
Rick
Join Date: Oct 2010
Posts: 1,016
Rep Power: 26 |
Hi,
You are right for the roughness height, but roughness constant isn't relative roughness: fluent uses this parameter to specify uniformity of roughness: since there is no indication on how to calculate it, you have to try and see if your simulation results approximate your experimental results; roughness constant=0,5 indicates a uniformal roughness; use values between 0,5 and 1 to specify non uniformal roughness. Daniele Last edited by ghost82; February 25, 2012 at 03:44. |
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February 24, 2012, 16:54 |
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#3 |
New Member
Paul
Join Date: Feb 2012
Location: CT
Posts: 6
Rep Power: 14 |
Thank you Daniele, I appreciate your very quick responds.
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