For example, on the quay of a remote island facing to the ocean without offshore breakwaters, it is necessary to deal with a multidirectional irregular wave field excelling in nonlinearity in order to obtain the amount of fluctuation of moored ship. By the way, in the analysis of the mooring motion of a moored ship in a conventional harbor, the fluid force acting on the ship is treated as a frequency response function, and it is time evolutionally solved after considering the nonlinear external forces of the fender and the mooring cable. In that case, generally the response of the vessel in the linear unidirectional irregular wave is solved and the cross-sectional shape of the hull is approximated by a function that satisfies the vessel specifications. On the other hand, the method to directly calculate the fluid force acting on a ship by three-dimensional fluid field analysis is capable of reproducing a wave field with a high nonlinearity, and it is not necessary to approximate the shape of the vessel by a function, but its application have been usually studied only in two-dimensional cross section and unidirectional waves. Therefore in this study, we propose a new method to simulate a moored floating body fluctuation in three-dimensional fluid field by using CADMAS-SURF/3D, whose functions are expanded with both generating nonlinearity of multi- directional irregular waves and realizing mooring analysis of mooring vessels of arbitrary shape.
At first, we show that we can realize multi-directional irregular wave generation in CADMAS- SURF/3D with practical enough accuracy by comparing the time series waveform, wave statistics, directional spectrum at the same point calculated by NOWT-PARI and CADMAS- SURF/3D, respectively. Next, CADMAS-SURF/3D is expanded so as to handle the motion of the ship, and the amount of mooring and mooring cable tension of the moored ship in one-way irregular wave and multidirectional irregular wave are calculated. Moreover, by comparing these calculation results with experimental results to verify their validity, a new moored ship fluctuation analysis model applying the expanded CADMAS-SURF / 3D to deal with arbitrary wave field and ship shape is proposed. Finally, we analyze a medium-size ship motion anchored to an actual quay in a remote island surrounded by multi-directional irregular waves.

Key Words: motions of moored ship, multi directional irregular waves, CADMAS-SURF/3D, Boussinesq model, Single-component wave approximation, calmness of harbor