Manning's Formula for Gravity Flow
Manning's equation for calculating gravity flow in open channels
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Manning's equation can be used to calculate cross-sectional average velocity flow in open channels
v = kn / n R2/3 S1/2 (1)
where
v = cross-sectional average velocity (ft/s, m/s)
kn = 1.486 for English units and kn = 1.0 for SI units
A = cross sectional area of flow (ft2, m2)
n = Manning coefficient of roughness
R = hydraulic radius (ft, m)
S = slope of pipe (ft/ft, m/m)
Hydraulic radius can be expressed as
R = A / P (2)
where
A = cross sectional area of flow (ft2)
P = wetted perimeter (ft)
The volume flow in the channel can be calculated as
q = A v = A kn / n R2/3 S1/2 (3)
where
q = volume flow (ft3/s, m3/s)
A = cross-sectional area of flow (ft2, m2)
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Related Topics
- Fluid Mechanics - The study of fluids - liquids and gases. Involves various properties of the fluid, such as velocity, pressure, density and temperature, as functions of space and time.
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Related Documents
- Hazen-Williams Equation - calculating Friction Head Loss in Water Pipes - Friction head loss (ftH2O per 100 ft pipe) in water pipes can be estimated by using the empirical Hazen-Williams equation
- Manning's Roughness Coefficient - Manning's roughness coefficient values for some common materials
