64
S = slope of the channel
n = surface roughness
K = constant dependent unit (k = 1 in SI system, and K = 1.49 in FPS system)
Surface roughness varies for different materials. For concrete, the value of “n” is
around 0.014 and the value varies for different materials, exact value of which can
be empirically evaluated. But many common materials’ values are available in the
literature (Nassehi and Das 2007).
Both formulae are empirical; however, Manning’s equation is more widely used
as it is more accurate.
Design of channels with incorrect theoretical knowledge or maintenance after
construction of channels may often result in obstruction to free flow of channels. In
the case of storm water drains, obstructions could result in stagnation of water that
can become a mosquito-breeding place (Fig. 2.9).
2.4.4 Flows Around a Body
Fluid flow around a body placed in a flow channel develops eddies (current of fluid
running contrary to the main current).
Fig. 2.9 Obstruction to
free flow of storm water
drains could result in
stagnation of water and
becoming a mosquitobreeding place
2 Fundamentals of Physics for Environmental and Medical Professionals
S = slope of the channel
n = surface roughness
K = constant dependent unit (k = 1 in SI system, and K = 1.49 in FPS system)
Surface roughness varies for different materials. For concrete, the value of “n” is
around 0.014 and the value varies for different materials, exact value of which can
be empirically evaluated. But many common materials’ values are available in the
literature (Nassehi and Das 2007).
Both formulae are empirical; however, Manning’s equation is more widely used
as it is more accurate.
Design of channels with incorrect theoretical knowledge or maintenance after
construction of channels may often result in obstruction to free flow of channels. In
the case of storm water drains, obstructions could result in stagnation of water that
can become a mosquito-breeding place (Fig. 2.9).
2.4.4 Flows Around a Body
Fluid flow around a body placed in a flow channel develops eddies (current of fluid
running contrary to the main current).
Fig. 2.9 Obstruction to
free flow of storm water
drains could result in
stagnation of water and
becoming a mosquitobreeding place
2 Fundamentals of Physics for Environmental and Medical Professionals