ABSTRACT
It can be inferred that if the roughness characteristics of commercial pipes are similar to those of the Nikuradse pipes, then the flow patterns and A-R curves will also be similar. Here, however, we encounter a difficulty because commercial pipes have a non-uniform and irregularly distributed type of roughness, which is very different to the uniform roughness created by Nikuradse. This means that, whilst the smooth and rough pipe laws would almost certainly still be valid, the curve in
the transitional zone might be expected to differ quite appreciably. The importance of any variation in this zone is accentuated by the fact that nearly all commercial pipes, especially when new, are found to operate within it.
