[Joachim]

Hey all!

I recently implemented Lund's boundary condition in OpenFOAM.
The BC seems to work just fine, but for some reason, my velocity profile is not that great.

Initially, I used exactly the parameters described in the original paper (same mesh, (y+=1.2, ...) second order accuracy), but I got pretty bad results (see Fig. 1).

Then, I decided to refine the mesh (basically refine the mesh in each direction by a factor 2 -> y+=0.5, ...), and obtained the results shown in Fig. 2.

For these simulations, I use the simple Smagorinsky model, with and without Van Driest damping functions to evaluate its impact on the solution (pretty significant!). I also tested the local dynamic Smagorinsky model, but the results were not that great (skin friction underestimated).

As seen in Fig. 3 and 4, it seems that the boundary condition has been correctly implemented. We can see the self-similar solution between inlet and recycled plane for the inner and outer layers. However, the simulation does not converge towards the correct profile (in Fig. 1 and 2)!

The fine simulation is not that bad, but several people (Jewkes, Lund, etc) obtained very good results on the exact same case on a way coarser grid (the first one)!

Has anyone already faced similar issues with LES in OpenFOAM? Where could this come from?

Thank you very much for your time!

Joachim