Absolute Roughness
Absolute roughness, abbreviated as \(\epsilon\) (Greek symbol epsilon), is a measure of the roughness of the inside of a flowing pipe. It is used in conjunction with the inside diameter to calculate the friction factor using a Moody Diagram, the Reynolds Number and the Darcy-Weisbach Equation.
Common values for the absolute roughness are listed below.
Absolute Roughness |
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Type of Pipe | Absolute Roughness in Feet | Absolute Roughness in Inches |
Drawn tubing (glass, brass, plastic) | 0.000005 | 0.00006 |
Commercial steel or wrought iron (new) | 0.00015 | 0.0018 |
Commercial steel or wrought iron (existing) | 0.0005 | 0.006 |
Cast iron (asphalt dipped) | 0.0004 | 0.0048 |
Galvanized iron | 0.0005 | 0.006 |
Cast iron (uncoated) | 0.00085 | 0.0102 |
Wood stave | 0.0006 to 0.0003 | 0.0072 to 0.0036 |
Concrete | 0.001 to 0.01 | 0.012 to 0.12 |
Riveted steel | 0.003 to 0.03 | 0.036 to 0.36 |
Tags: Flow Equations