	Product(s):	WaterGEMS, WaterCAD, HAMMER, SewerGEMS, SewerCAD, CivilStorm
	Version(s):	CONNECT Edition, V8i
	Area:	Modeling

Problem

Difference between the coefficients e and f, when using the Darcy-Weisbach friction method?

What is the difference between roughness height 'e' and Bed Roughness 'Ks' or Colebrook-White 'K'?

Solution

e = roughness height (length units such as mm)
Ks = roughness height or "bed roughness" - equivalent to the Darcy-Weisbach 'e' (if you want to use Ks, use the Darcy-Weisbach friction method)
K =
f = friction factor (unitless)

The values of e and f are not interchangeable.

The relationship between e and f can be obtained from the Colebrook-White Equation and the Swamee-Jain Formula

For details see Page 31 to 35 of the book Advanced Water Distribution Modeling and Management.

What is the difference between Darcy-Weisbach roughness coefficients e and f, and Bed Roughness Ks o

Problem

Solution

See Also