2.3 Swell Propagation Simulation by Characteristics Method
41
Fig. 2.2. Change of relative average wave heights along a meridian for different
generation area b.1J at latitude 6-80°
= mo ~ {(3 _ 2 cos
2 ( 371
cos 2 ('Po) 2
4
1
{3,
cos 4 ( +
-+
+ - -
cos4( cp0 )
8
4
32
'
!32
(2.17)
where m0 is the zero moment for the boundary value of the spectrum (2.15).
It should be noted that the average wave period calculated with the help
of the second-order moment (T = 271Jm2 /m0 ) coincides with its value at
the boundary. The function value in the brackets of (2.17) is changed with
increasing distance between the observation point and the boundary. It includes equally both the second-order moment and the zero-order moment.
Thus, the average wavelength, calculated using appropriate moments, can be
different.
The angle (31 is determined numerically using the ratio (2. 7) for the case
cp = 60° and rJ = ( 13J. + 132) at (32 = 371 - {31 . Then the numerical values
of the expression (2.14) are determined. The calculated results for different
angles are shown in Fig. 2.2. As it is seen, the height is decreased with the distance from the source and wave approaching the Equator. Furthermore, the
heights of waves propagating from small non-extended sources, are decreased