question about grid convergence study
 

hi dear foamer
i have a small question about gird convergence study

If what I know is right in grid convergence study
Wall Y+ or initial cell spacing from wall for boundary layer resolution should be same for all levels of grid (i.e. Coarse, Medium, Fine, etc.).
(They offer only the first cell size)

so this is my question
Is there no need to match the total layer thickness or expansion ratio and the number of layers in coarse, medium, fine gird system?

Another question is
To check the grid convergence, a uniform mesh must be created from coarse, medium, and fine, but I know that snappyHexmesh creates a non-uniform mesh.
Is there a way to do grid convergece for non-uniform cases or assuming they are generated uniformly?

I would really appreciate it if you could give me the answer.