Transient Surge Motion Of A Moored Ship In Random Waves

A ship in waves is subjected to second-order wave forces as well as to linear oscillatory ones. The second-order force contains slowly varying components, of which the characteristic frequency can be as low as the natural frequency of horizontal motions of moored ships. As a consequence, the slowly varying force can excite a moored ship to undergo unexpectedly large horizontal excursions, which may result in serious damages to its mooring system. Many investigators have tackled this problem under respective interests. For publications up to 1982, readers are referred to the comprehensive review article of Ogilvie (1983). Agnon et al. (1988) rigorously examined shallow-water effects on the slow drift motion of a floating cylinder by using multiple-scale expansion techniques in both time and space. They clarified under which conditions the slow motion can be large. Choi and Kim (1989) applied the method to a slender ship in beam seas, Our primary concern here is focused on the second-order slowly varying drift force on and the transient surge motion of a moored ship in random head seas. In this paper, we include only the second-order incident waves among second-order potentials. More attention has been paid on the role of the time-memory effect on the surge motion of a moored ship in head seas. F= L L Is-II)IIS-}')*I ~jcos{-(w; -Wj )t+£; -£j} 1 ]