Sand grain roughness?
 

Hello,

I would like to add roughness to a wall, I am not sure what sand grain roughness is trying to represent. Can anyone tell me how this correlates to absolute roughness? If my absolute roughness of my wall is 0.000125 inches what will my sand grain roughness be?

Thanks

Hopefully this helps!! you will need to go thru some literature though.

http://ijmem.avestia.com/2012/PDF/008.pdf

I too need to create rough surface in ANSYS geometry. how can it be done?

CFX has a wall roughness model in several turbulence models. Read the documentation for details.