[Edolig]

Hi everyone,

I have a quite theoretical question about how the wall functions for k, omega and nu work in Openfoam.

In my simulations I m using:
-kqRWallFunction
-nutkWallFunction
-omegaWallFunction

With k-w sst


I’have consulted many sources and many times I’have found that the desired y+ when using wall functions should be y+>30 so that the first cell is in the log region and so on.

In my simulations I have evaluated the first cell height in order to have an y+>30 even though then in the simulations the practical average values are always lower than 30 (between 15-25 depending on the refinement of the mesh). At the same time I can’t increase the height to much because the layers would collapse. I’m a bit tied up.

Now my question is:
If the average y+ is lower than 30(between 10-20) in the simulations is it a huge problem? Because according to a source that I have consulted, in Openfoam the wall functions are implemented in such a way that they can adapt on necessity allowing to have also y+<30 without producing too much error.

I would like to have a clarification about how they work in Openfoam and if it’s ok to have the average lower than 30 or there is the risk to introduce too much error.

Thank you very much for your kind help!