Rh = hydraulic radius of the conduit (m, ft)
S = slope of the conduit (m/m, ft/ft)
In general the Chezy coefficient - C - is a function of the flow Reynolds Number - Re - and the relative roughness - ε/R - of the channel. ε is the characteristic height of the roughness elements on the channel boundary.
The Manning empirical relationship is one way to estimate the roughness coefficient C:
C = (1 / n) Rh1/6
n = Manning coefficient of roughness
For concrete walls in conduits it's common to use C = 50 (m1/2/s).
A rectangular 1 (m) x 1 (m) concrete conduit with slope 1/100 (m/m) is half filled with water.
The cross sectional area of the filled conduit can be calculated as
A = 0.5 * (1 m) * (1 m)
= 0.5 m2
The wetted perimeter of the filled conduit can be calculated as
P = 2 * 0.5 * (1 m) + (1 m)
= 2 m
The hydraulic radius can be calculated as
Rh = A / P
= (0.5 m2) / (2 m)
= 0.25 m
The velocity in the flow can be calculated using eq. (1) as
v = (50 m1/2/s) ((0.25 m) (1/100 m/m))1/2
= 2.5 m/s
The volume flow can be calculated as
q = A v
= (0.5 m2) (2.5 m/s)
= 1.25 m3/s
The study of fluids - liquids and gases. Involving velocity, pressure, density and temperature as functions of space and time.
Geometric relationships like area, wetted perimeter and hydraulic diameter.
Imperial (USCS) and SI dimensions and units terminology in fluid mechanics.
Calculate cross-sectional average velocity flow in open channels.
Convert slopes pitch between degrees, gradients and grades.
Mechanical production methods and their surface roughness.
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