ssc-367 - Ship Structure Committee

A.4.1
Wave Hindcastinq
Wave hindcasting is a term used to describe the process of estimating
the random sea characteristics of an area based upon meteorological
or wind data. Various researchers (ReferencesA.2, A.4, A.6, A.7 and
A.8) have attempted to derive a relationship between the wind speed
over a recent period of time and the spectrum of the random sea
generated by the particular wind. The wind speed data is usually
qualified by two additional parameters, the duration that the wind
has been blowing at that speed and the fetch or distance over open
ocean that the wind has been blowing.
A set of equations as derived by Bretschneider (ReferenceA.2), which
relate wind speed, duration and fetch are as follows.
g*H#
= 0.283*tanh[0..125*(g*F/Uz)””42]
g*Ts / (2r*U) = 1.2*tanh[0.077*(gF/U2)””42
...
g*t minl” =
6.5882*exp{[0.161*A2-0.3692*h+2.024]%
+ O.8798*A}
where
u
is the wind speed,
F
is the fetch,
A
= ln[g*F/U2],
t min
is the minimum duration for which the fetch will
determine the significant height and period, and
tanh
is the hyperbolic tangent.
A-17
-) s“