Roughness height and Y+ and y
 

Hello

I am modeling a concrete channel by Fluent.
What is Roughness height and Y+ and y in defining concrete channel?
I am confused what they are? I read all thread about thats but i don't know what they are.
Is the Roughness height exactly the height found on standard charts (http://www.engineeringtoolbox.com/su...cts-d_209.html)

thanks