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

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

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)
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.

How do you find or change the friction method used in WaterGEMS and WaterCAD

Selecting the Gravity Friction Method in SewerGEMS and CivilStorm

Difference between Colebrook White and Darcy Weisbach coefficients

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