# Rough wall

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November 9, 2009, 11:59
Rough wall
#1
New Member

Bruyère
Join Date: Oct 2009
Posts: 9
Rep Power: 9
Hello everybody,

Do you have any experience about the rough wall treatment. I want to run simulations with smooth and rough wall : it deals a throttle pressure loss. My problem is to know if I can set as a CFX roughness height hs, the roughness height that I got from a test measure. my measure corresponds to a roughness depth of 1.6 um. So Can I set hs=1.6 um in CFX?

Nota : Sandgrain diameter is hs in CFX : have a look at cfx help about rough wall treatment.

nellio75
Attached Files
 RoughWallTreatment.doc (41.0 KB, 89 views)

 November 17, 2009, 04:07 #2 Senior Member   Join Date: Nov 2009 Posts: 125 Rep Power: 9 Try the following: 1) Insert a 'Boundary' within your Domain 2) Change 'Boundary type' to 'Wall' 3) Goto 'Boundary Details' tab 4) Expand the 'Wall Roughness' option 5) insert your hs in the 'Roughness Height' in meters __________________ Thank you for your kind attention. Kind regards, mactech001 Currently using: ANSYS v13

 November 18, 2009, 10:03 height of the sand grain #3 New Member   Bruyère Join Date: Oct 2009 Posts: 9 Rep Power: 9 Thanks for your reply but I'm afraid my question wasn't very understandable : if you have looked at the attached file, I 'm looking for an equivalence between a real measure of a wall roughness and the diameter of a sand grain used in CFX: the sand grain layer is used in CFX to modelise the roughness. Anyway, in the meantime, I've found an extract of a book where there's an example of different real roughness. I think it will be sufficient for the purpose of my study. So I can close my question for this forum. Anyway, I thank you for having paid attention of my question. Best Regards nellio75

 November 19, 2009, 01:12 #4 Senior Member   Join Date: Nov 2009 Posts: 125 Rep Power: 9 Hi nellio75. glad you've found a possible solution. would you mind sharing info on the real roughness please? __________________ Thank you for your kind attention. Kind regards, mactech001 Currently using: ANSYS v13

November 19, 2009, 06:23
#5
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Bruyère
Join Date: Oct 2009
Posts: 9
Rep Power: 9

Best Regards
Nellio75
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 equivlence_schlichting.jpg (90.4 KB, 175 views)

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