ssc-367 - Ship Structure Committee

9 is the acceleration of gravity in units compatible
with .thevelocity units. .’
The energy of, or area under the curve of the sea spectrum must
remain constant.
f$e(@*dwe = fS(w)*du
Taking the derivative of the encounter frequency equation gives the
following.
dwe = [1 + 2Vw/g]*dw
Substituting the derivative
following.
nto the area ntegral gives the
f$e(ue)*[l +2Vw/g]*dw = ~S(w)*dw
Therefore, equating the integrands gives the relationship between the
encounter spectrum and the stationary sea spectrum.
Se(we) = s(l.u)/[l+2vw/gl
This equation is required to transform a stationary sea spectrum to
an encounter spectrum for the purpose of intergrating the responses.
However, if only the response statistics are desired, and not the
actual response spectrum, then the same substitutions as above can be
made.
se = s/[1 +2vw/g]
dwe = [1+2VU /g]*du
B-10
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