phase shift in the wave load.
Equation 3.37 and figure 3.12 show that with respect to the motional behavior of this cylinder three frequency areas can be distinguished:
1. the low frequency area (!2 ¿ c=(m + a)), with motions dominated by the restoring spring term,
2. the natural frequency area (c=(m + a) . !2 . c=a), with motions dominated by the damping term and
3. the high frequency area(!2 À c=a), with motions dominated by the mass term.
Also, equation 3.37 shows that the vertical motion tends to the wave motion as the frequency decreases to zero.
Figure 3.13 shows the speed dependent transfer functions of the roll motions in beam waves and the pitch motions in head waves of a container ship. Notice the opposite e¤ect of forward speed on these two angular motions, caused by a with forward speed strongly increasing lift-damping of the roll motions.