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1 point

·
13th Dec 2022

This is the hydraulics bible.

https://www.amazon.com/Open-Channel-Hydraulics-Ven-Te-Chow/dp/1932846182

1 point

·
20th Apr 2015

Hey man, you are basically right. DW's f and Mannings n both are measure of the roughness of the bed while Cezy's C is a factor of the waters ability to flow. However, this is not particularly profound as Chezy's C and DW's f are both placeholder variables defined by other factors and C is basically the inverse(and a few other things) of f. A very simplified explanation:

Chezy: u=C(RS)^(1/2)

DW: u=(8gRS/f)^(1/2)

So we can say: C=(8g/f)^(1/2)

It is important to remember also that Manning's equation is empirical (derived from experimentation rather then physical laws) and is in fact dimensionally inconsistent, one of its major criticisms.

The Chezy equation and the Darcy Weisbach equation can both be related to the conservation of momentum around a control volume. Which would be too difficult to explain over reddit but there's pretty good reading out there about it.

Check out the book: Open Channel Hydraulics (Chow, 1959). It's basically the bible of open channel flow and is used as a reference in many modern 2D and 3D flow and sediment transport models. You can also find a free and possibly illegal version here.

MIT also provides a pretty good summary of the three primary OCF roughness equations here.