Manning's coeff to absolute roughness

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SUMMARY

The equation relating absolute roughness to the Manning coefficient is defined as n = k1/6/26, where n represents the Manning roughness coefficient and k denotes absolute roughness in millimeters. This equation is referenced from Webber's 1971 publication, "Fluid Mechanics for Civil Engineers." When applying this equation to a Manning coefficient of 0.011 for epoxy lined Ductile Iron Pipe, the calculated absolute roughness (k) is approximately 0.000001795477 feet. This value aligns with typical roughness values for commercial steel pipes, confirming its accuracy.

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  • Understanding of Manning's equation and roughness coefficients
  • Familiarity with fluid mechanics principles
  • Knowledge of pipe materials and their properties
  • Ability to perform unit conversions between metric and imperial systems
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  • Research the application of Manning's equation in various pipe materials
  • Learn about the impact of surface roughness on fluid flow
  • Explore additional references on fluid mechanics, particularly Webber's 1971 work
  • Investigate methods for measuring absolute roughness in practical scenarios
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Civil engineers, hydraulic engineers, and anyone involved in fluid mechanics or pipe design will benefit from this discussion, particularly those focused on calculating and optimizing flow characteristics in piping systems.

Danger86514
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Does anyone have the equation that the absolute roughness is expressed in terms of Manning coefficient, with the reference included?

I have found one from Webber 1971.

n = k1/6/26

where:
n = applicable Manning roughness coefficient,
k = absolute roughness (mm)

Reference :Webber, N.B. (1971) Fluid Mechanics for Civil Engineers. Chapman & Hall.

when I apply this equation to Manning coefficient of 0.011 (epoxy lined Ductile Iron Pipe)

I get an sbsolute roughness (k) = 0.000001795477 ft.

I need some confermation on the value and equation
 
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Danger86514 said:
Does anyone have the equation that the absolute roughness is expressed in terms of Manning coefficient, with the reference included?

I have found one from Webber 1971.

n = k1/6/26

where:
n = applicable Manning roughness coefficient,
k = absolute roughness (mm)

Reference :Webber, N.B. (1971) Fluid Mechanics for Civil Engineers. Chapman & Hall.

when I apply this equation to Manning coefficient of 0.011 (epoxy lined Ductile Iron Pipe)

I get an sbsolute roughness (k) = 0.000001795477 ft.

I need some confermation on the value and equation

The one you have from Webber is the only one I know of. The value you calculated for the roughness (k) seems reasonable. A commercial steel pipe has a roughness of about 0.00015-ft, so I imagine an epoxy lined one would be even less like you have determined.

CS