Area of 1 blade × velocity of the current in ft. per sec.
----------------------------------------------------------
400
× by the square of difference of velocities of current and wheel
periphery = the horse power; or
A × V 2
------ × (V - v) = h. p.
400
[TEX: \frac{A \times V}{400} \times (V - v)^2 = h. p.]
in which A equals the area of blade in square feet, V and v velocities
of current and wheel periphery respectively, in feet per second. Thus,
for example, a wheel 10 feet in diameter with blades 6 feet long and 1
foot in width, running in a stream of 5 feet per second--assuming the
wheel to be giving as much power as will reduce its velocity to one half
that of the stream--the figures will be
6' × 5' 2
------- × 2.5 = 0.468
400
[TEX: \frac{6' \times 5'}{400} \times 2.5^2 = 0.468]
horse power of the wheel.