energy flux per unit wave
dicular to wave advance is
crest width transmitted across a plane perpenP = EnC = EC, .
(2-40)
Energy flux P is frequently called wave power and
47rd/L
sinh (4îrd/L)
If a plane is taken other than perpendicular to the direction of wave
advance, P = ËC sin , where is the angle between the plane across
which the energy is being transmitted and the direction of wave advance.
For deep and shallow water, Equation 2-40 becomes
P = — E„C (deep water) .
o
2 ° °
r
(2-41)
P = EC? = EC (shallow water) .
(2-42)
An energy balance for a région through which waves are passing will
reveal, that for steady State, the amount of energy entering the région
will equal the amount leaving the région provided no energy is added or
removed from the System. Therefore, when the waves are moving so that
their crests are parailel to the bottom contours,
or, since
EonoCo = EnC .
1
” 2 ’
\ ËOC„ = ËnC .
(2-43)
When the wave crests are not parailel to the bottom contours, some parts
of the wave will be traveling at different speeds, the wave will be
Equation 2‘4Î does not apply. (See Section 2.3. WAVE
REFRACTION.)
The following problem illustrâtes some basic principles of wave energy
and energy flux.
r
2-28