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.
|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|
|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