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Figure 5.37 Dissipation
dis
(denoted as
in this figure) versus distance to the surface
z
in wall-layer
coordinates. The vertical line represents the dissipation level in the boundary layer over a solid wall.
Figure is reproduced from
Young & Babanin
(
2006a
) © American Meteorological Society. Reprinted
with permission
dis
κ
z
=
1
(5.72)
u
3
∗
w
shown by the vertical line in the figure. The enhancement of the dissipation rates compared
to the wall layer is obvious. Maximal values of the enhancement are up to 200 times greater
than the wall-layer magnitude (even greater than those in
Agrawal
et al.
(
1992
) where they
were up to 70 times).
Dissipation of the energy of wind-generated waves in the finite-depth water column, that
is in the Lake George conditions, consists of two parts: turbulent kinetic energy dissipation
D
a
(5.67)
, which would occur in the deep water as well as in finite depths, and dissipation
per unit area due to bottom friction
B
a
. The total dissipation
T
a
T
a
=
D
a
+
B
a
≈
I
a
(5.73)
should match the wind energy input per unit area
I
a
for steady wind-wave conditions.
Technically speaking, some of the wave energy dissipated from the waves does not neces-
sarily convert into turbulence and may be spent on, for example, work against buoyancy
forces when the bubbles are entrained into the water in the course of wave breaking. Such
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