There is an error in the original paper in the description of the applicability range for Eq. (9) that could misguide the reader. The valid range of Eq. (9) is Ra/Dh > 0.0028.

On page 8, in the paragraph following Eq. (9), the statements on the applicability of the correlation should read:

“This correlation is only valid for Ra/Dh > 0.0028 as values below this threshold result in a negative ks/Dh. Relative equivalent sand grain roughness should be assumed to equal zero for Ra/Dh < 0.0028.”