Dear Frank, I have already answered that in my previous answer: “Where the level 5-mesh (could be a higher refinement level) must be fine enough to comply with your turbulence model’s y+ requirements (30 to 150)”. So the first cell near the wall must be between 30 to 150 (y+) for the SST-k-omega model. If you do not know what y+ is, there is plenty of material to study from, i.e. What is y+ (yplus)?. The height of the first cell defines the “density” of subsequent lower levels.