simulation of effect surface roughness on aifoil
 

hi.
I want to examine the effect of roughness on the surface of the airfoil But i have several questions on this topic.
1.how much the height of first cell to roughness height ks=0.5mm and ks=1mm and ks=0.3mm and ks=0.1mm and ks=0.03mm?
2.how much the wall yplus for simulation roughness?
3.For high roughness height, constant speed, constant Reynolds, how can we increase dimensionless parameter roughness (ks + = ρ * ks * (u *) / μ)
4.Is there a relationship between the amount yPlus and dimensionless parameters for the simulation of roughness and roughness?
5.How do I know that I've done that simulates the roughness is true?

The results of numerical simulations of the airfoil with smooth surface with results published an article that did have one

Thank you

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