264
CONTINUOUS SYSTEMS
25
20
15
10
5
0.8
1.2
1.6
Frequency œ, rad/sec
Figure 10.10 Water wave amplitude spectra for a spread-moored LST (after
O'Brien and Muga, 1964).
Frequency cù, rad/sec
Figure 10.11 Force amplitude spectra for port bow chain No. 2 of an LST (after
O’Brien and Muga, 1964).
To investigate possible bow chain résonance due to parametric excitation,
choose a driving frequency ü> = 0.65 rad/sec, or the frequency at the highest
concentration of energy for the wave. With the data and équations (10.65), the
characteristic parameters are
ôn = u/J/ü2 = (l.lln)2/(0.65)2 = 2.92n2
=
= 0.5(2.92n2) = 1.46n2 (maximum)