[nellio75]

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
nellio75

[mactech001]

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]

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

[mactech001]

Hi nellio75.

glad you've found a possible solution.

would you mind sharing info on the real roughness please?

[nellio75]

Please find attached the extract of the book as asked.

Best Regards
Nellio75