Manning's coeff to absolute roughness

  • Thread starter Thread starter Danger86514
  • Start date Start date
  • Tags Tags
    Absolute
Join the discussion
Registration is free. Ask a follow-up in this thread, or start your own.
Sign up Log in
1 reply · 18K views
Danger86514
Messages
12
Reaction score
0
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
 
Engineering news on Phys.org
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