I am performing a high speed simulation with a normal shock of about Mach 1.5 (Model - k-w sst). I need to resolve the boundary layer close to the wall in order to predict flow separation.
I have an experimental velocity profile at a certain location that needs to be matched. I first did the simulation with zero roughness height and the y-plus was about 0.9-1 (which I believe is what I need), but I couldn't get the same experimental profile. By experimenting with different non-zero values for roughness height (same mesh) I was able to somewhat match the profile, but the wall yplus was above 100. Decreasing the first wall height didn't make a difference. And by this time I had realized, my roughness height is way higher than the first cell height (which I found out was non-physical)
So I read the documentation that a non-zero roughness height would shift the wall to half the roughness height. If that is so, from where is the yplus being calculated? The actual wall or the shifted virtual wall?