The problem of a floating body moving with arbitrary oscillating motions and arbitrary" wave directions is modified. Under the assumptions of potential flow and low moving speed, the Green function is expanded into an oscillating source G O at zero forward speed and a correct term G∼ to take into account low moving speed. It is shown that the present form of Green function gives good numerical calculation performance while wave damping effects are considered. This method can also be applied to calculate wave loads, added wave resistance and wave damping forces. The effects of currents to a floating body are be discussed as well.
In designing a single-point mooring system, it is important to consider wave damping effects while the mooring force exerting in the system is evaluated. To examine the effects, the motions of a floating body should be known. These motions can be described by obtaining various forces acting on the floating body. Over the recent two decades, many researchers have studied wave exciting force problems. Different approaches have been adapted and many numerical models have been developed. Some of the results have even been applied to the preliminary design of a floating system in ocean engineering. Wichers & Van Sluijs (1979), Wichers (1982,1984), Wichers & Van den Boom (1983), Faltinsen, Dahle & Sortland (1987), Faltinsen & Mmsens et al (1980), Faltinsen & Sortland (1987), Takagi, Nakamur & Saito (1984), Chakrabarti (1982), Wichers (1986), Hearn & Tong (1987), and Lee & Sun (1997) have studied the relationship between wave drift damping and wave exciting threes. The main conclusions from their findings are 1) Measured damping coefficient is larger in waves than that in calm water when a floating body oscillates in low frequency modes.
