[CellZone]

Hi everyone,

I struggle choosing the right wall functions. I am using SST in my simulation, since it combines the advantages of k-epsilon and k-omega. As far as I searched for wall functions and SST in this forum I found:

http://www.cfd-online.com/Forums/ope...ion-usage.html

nutUSpaldingWallFunction (standard for SA turbulence model, called nutSpalartAllmarasWallFunction in earlier version, original reference is doi:10.1115/1.3641728):
continuous wall-function which should cover the complete y+ range from O(1) to somewhere of O(10). Might be the best choice (together with low Re kEpsilon, kOmegaSST or SA, when y+ varies for different parts of the wall.

https://www.comsol.com/blogs/which-t...d-application/

Finally, the SST model is a combination of the k-epsilon in the free stream and the k-omega models near the walls. It does not use wall functions and tends to be most accurate when solving the flow near the wall.

http://www.cfd-online.com/Forums/ope...estigated.html

Note that the k-omega SST model we provide is in high-Re form and does not include the wall-damping terms often included in the k-omega model for near-wall and low-Re flow. However, you can still use the k-omega SST model for low-Re and near wall flow for a range of resolutions if you use a continuous wall-function (which in OpenFOAM-1.7.x is named nutSpalartAllmarasWallFunction for historical reasons) and this should be used as the wall BC in nut. The BC of k for the continuous wall-function should be kqRWallFunction.

I am wondering now: one source says SST uses wall functions, one says: no . So one is wrong or do I confuse anything?

The range of my y+ values are for a really fine grid on some walls 0.01 and on other walls y+=45.

So when I use nutSpalartAllmarasWallFunction , what range should my y+ be?

Member vkrastev says:

Well, the good news are that the SST model CAN actually be employed to resolve boundary layers with y+<1 (as it is supposed to), both with the omegaWallFunction BC as well as with directly imposing Menter's BC for the viscous sublayer.

So my y+ value does not play a role when using nutSpalartAllmarasWallFunction ?

Could someone bring light into the dark (dark for me).

By the way: currently I am using mutkWallFunction which makes trouble for very fine meshes with SST. So that's why I have doubts about it.

Sorry I am a rookie in CFD :-/

Thank you guys!