Page 115 - Pipelines and Risers

88 Chapter 6

w, Angular frequency of spectral peak
g Acceleration due to gravity
ap Phillips' constant

o Spectral width parameter
y is the JONSWAP peakedness parameter determined from
1,
(6.11)

Y >5

Figure 6.3 Wave spectrum.

From the wave spectrum we can find several properties. k denotes the nh (stress) spectral
moment defined by:

(6.12)
H1/3 is the significant wave height and can be found as:

HI,, =4K (6.13)
T, = -,/: (6.14)
The characteristic wave period Tw may be estimated as:
IT;-

and the spectral band width parameter E as:
I -2
(6.15)

By performing an inverse transformation, the wave amplitudes (ai) and frequencies (@ ) of
each wave component is extracted from the wave spectrum.