Fluid Flow Table of Contents  Hydraulic and Pneumatic Knowledge
Fluid Power Equipment
Open Calculator to determine the open channel fluid flow 
Open channel fluid flow Calculator & Manning's Roughness Coefficient
Manning's equation, which is based on Chezy's equation, is a common method to calculate the free surface flow or fluid flow within a channel.
For Manning's equation, the roughness coefficient in Chezy's equation is calculated as:
C = k [ R^{(0.125) }/ n]
Where:
C = Chezy's roughness coefficient (ft ^{1/2}/sec, m ^{1/2}/sec)
R = Hydraulic Radius (ft, m)
n = Manning's roughness (s/m^{1/3})
k = Constant (1 m^{1/3}/m^{1/3}, 1.49 ft^{1/3}/ft^{1/3})
Substituting the calculated roughness into Chezy's equation, one can obtain Manning's equation:
Q = [k / n] A R^{2/3 }S^{1/2}
Where:
Q = Discharge (ft^{3}/sec, m^{3}/sec)
k = Constant ( 1.49 ft^{1/3}/ sec, 1.00 m^{1/3}/ sec)
n = Manning's roughness coefficient
A = Flow area (ft^{2},m^{2)}
R = Hydraulic Radius (ft, m)
S = Slope Friction (ft/ft, m/m)
