Geoscience Reference
In-Depth Information
Figure 7.5 Mean velocity spectrum of incipient-breaking (solid line) and post-breaking (dashed line)
waves. The Kolmogorov interval slope of f 5 / 3 is shown. The text demonstrates values of respective
total dissipation rates D a ( 5.67 , denoted as D in this figure) and the integral of spectral dissipation
seen in Figure 7.3 . 95% confidence limits are shown with the vertical straight segments. Figure is
reproduced from Young & Babanin ( 2006a )
©
American Meteorological Society. Reprinted with
permission
not appear to differ significantly. The levels of the Kolmogorov intervals at higher frequen-
cies of the two spectra, however, are essentially different. At these frequencies and at the
20 cm depth, the turbulent velocities apparently dominate the orbital velocities. The dif-
ference between Kolmogorov intervals can be attributed to the loss of energy from across
the wave spectrum seen in Figures 7.3 and 7.4 . The total dissipation estimated from the
velocity spectra in Figure 7.4 and the wave spectra in Figure 7.3 should match:
F
df
(
f
) p
F
(
f
) i
D a i
D a p =
g
·
(7.20)
t
f
where
t is the time difference between the mean time points of subsequent breaking and
non-breaking segments and the overline represents the ensemble average. Here, the spectral
dissipation term is multiplied by g :
·
(
)
F
f
S ds (
) =
f
g
(7.21)
t
 
Search WWH ::




Custom Search