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nellio75 November 9, 2009 11:59

Rough wall
1 Attachment(s)
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.

Thanks in advance

mactech001 November 17, 2009 04:07

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

nellio75 November 18, 2009 10:03

height of the sand grain
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

mactech001 November 19, 2009 01:12

Hi nellio75.

glad you've found a possible solution.

would you mind sharing info on the real roughness please?

nellio75 November 19, 2009 06:23

1 Attachment(s)
Please find attached the extract of the book as asked.

Best Regards

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