ssc-367 - Ship Structure Committee

H~ = 0.1610*g/(um)2
‘m = o.4o125*g/(H#
An interesting point that may be noted is that if B
were set equal
to 0.75 instead of 0.74, the w would be the frequency
o
corresponding to the modal period, Tm.
A.3.3
JONSWAP and Related Spectra
The JONSWAP wave spectrum equation resulted from the Joint North Sea
Wave Project (Reference A.5). The JONSWAP equation is the original
Bretschneider wave spectrum equation with an extra term added. The
extra term may be used to produce a sharply peaked spectrum with more
energy near the peak frequency. The JONSWAP spectrum can be used to
represent the Bretschneider wave spectrum, the original Pierson-
Moskowitz wave spectrum, and the ISSC modified P-M spectrum. The
full JONSWAP equation is as follows.
s(w) = (aj*g2u5 ) *exp[-1.25*W/um-’)*ya
where:
a = exp [-**(M-Wm)2 / (U*WM)2]
‘m
is the frequency of maximum spectral energy.
The Joint
North Sea Wave Project recommended the following mean
values to represent the North Sea wave spectra.
Y = 3.3
0 = 0.07, for W