[amir.a.aliabadi]

Hello Dear OpenFOAM Community,

Is there a reference for the description of the value field for OpenFOAM wall functions? particularly for the types below with the following examples:

Thanks,
aaa

Example 1:

type kqRWallFunction;
value uniform 0.4;

Example 2:

type alphatJayatillekeWallFunction;
Prt 0.85;
value uniform 0;

Example 3:

type nutUSpaldingWallFunction;
value uniform 0;

[anishtain4]

It's just a placeholder, is not needed since the value will be either zero gradient (in your case) or zero (in case of y+<5).

https://github.com/OpenFOAM/OpenFOAM...FvPatchField.H

[amir.a.aliabadi]

Hi Dear Mahdi,

Thanks a lot. So since my y+ is somewhat large > 100 then the value field is automatically set to zerogradient, right? I am just wondering how is it possible to define a roughness length for the wall function to use. My surface roughness is about 5 cm and I want to supply this to the wall function. Do you have any suggestions?

By the way, you are in Canada too! we are at the University of Guelph. Will be happy to meet sometimes.

Regards,
Amir A. Aliabadi

[anishtain4]

Hi Amir,

Yes, you have y+>100 and you are using the kqRWallFunction, so it should be good.
For the roughness I think it doesn't affect k value at the wall, but the effect shows up at nut. To see a complete list of the available wall function for every variable check:
$FOAM_SRC/TurbulenceModels/turbulenceModels/derivedFvPatchFields/wallFunctions
There, under nutWallFunctions you will see some models with roughness. Hope that answers your question.

Yes, I'm at UNB, will surely contact you if I pass by there, or we might meet at a conference.

[amir.a.aliabadi]

Thanks a lot Mahdi!