Flow Section Channels  Geometric Relationships
Geometric relationships like area, wetted perimeter and hydraulic diameter.
Area, wetted perimeter and hydraulic diameter for geometric sections like
 rectangular channels
 trapezoidal channels
 triangular channels
 circular channels
Rectangular Channel
Flow Area
Flow area of a rectangular channel:
A = b h (1)
where
A = flow area (m^{2}, in^{2})
b = width of channel (m, in)
h = height of flow (m, in)
Wetted Perimeter
Wetted perimeter of a rectangular channel:
P = b + 2 h (1b)
where
P = wetted perimeter (m, in)
Hydraulic Radius
Hydraulic radius of a rectangular channel:
R _{ h } = b h / (b + 2 h) (1c)
where
R _{ h } = hydraulic radius (m, in)
Trapezoidal Channel
Flow Area
Flow area of a trapezoidal channel:
A = h (b + T) / 2 (2)
Wetted Perimeter
Wetted perimeter of a trapezoidal channel:
P = b + 2 (((T  b) / 2)^{2}+ h^{2}) ^{ 1/2 } (2b)
Hydraulic Radius
Hydraulic radius of a trapezoidal channel:
R _{ h } = ( h (b + T) / 2) / ( b + 2 (((T  b) / 2)^{2}+ h^{2}) ^{ 1/2 } ) (2c)
Triangular Channel
Flow Area
Flow area of a triangular channel:
A = z h^{2}(3)
where
z = see figure above (m, in)
Wetted Perimeter
Wetted perimeter of a triangular channel:
P = 2 h (1 + z^{2}) ^{ 1/2 } (3b)
Hydraulic Radius
Hydraulic radius of a triangular channel:
R _{ h } = z h / 2 (1 + z^{2}) ^{ 1/2 } (3c)
Circular Channel
Flow Area
Flow area of a circular channel:
A = D^{2}/4 (α  sin(2 α)/2) (4)
where
D = diameter of channel
α = cos^{1} (1  h/r)
Wetted Perimeter
Wetted perimeter of a circular channel:
P = α D (4b)
Hydraulic Radius
Hydraulic radius of a circular channel:
R _{ h } = D/4 [1  sin(2 α) / (2 α)] (4c)
Related Topics

Fluid Mechanics
The study of fluids  liquids and gases. Involving velocity, pressure, density and temperature as functions of space and time.
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