We discuss the validity of the existing theories for estimating the seakeeping qualities of high speed vessels. They are strip theory, high speed slender body theory, three-dimensional Green function method and Rankine panel method. The boundary-value problems of them are solved under the same linearization of uniform flow. Numerical results concerning the hydrodynamic forces and motion amplitudes in head sea conditions are compared with the experimental data. We have gotten the conclusion from comparative studies that, at present stage, the high speed slender body theory is the most useful and most accurate method for estimating the seakeeping qualities of a high speed boat.
Recently many kinds of high speed vessels have been developed and investigated. The performances of high speed vessels are strongly affected by wave loads. Therefore reliable estimation of seakeeping qualities is one of the most important tasks with respect to the development of high speed vessels. So far strip theory has been used as the main tool for estimating the performance of a ship in waves (Tasai and Takagi (1969), Salvessen et a/.(1970), Kobayashi et al.(1973)). However, its validity and limitation for high speed cases have not yet been investigated clearly. In this paper, we apply four existing theories, the strip theory, the high speed strip theory (Chapman (1975), Saito et a/.(1979), Yamasaki et a/.(1985), Faltinsen et al.(1991), Ohkusu et al. (1990, 1991, 1994)), the three-dimensional Green function method (Iwashita eta/.(1989)) and the Rankine panel/source method (Yasukawa (1990), Nakos et al.(1990), Takagi (1990), Lin et o2.(1993)), to a high speed boat. We evaluate the hydrodynamic forces and the motion amplitudes in head sea condition. We have also carried out three kinds of experiment, the forced oscillation tests, measurement of wave exciting forces and ship motion amplitudes to examine the accuracy of each theory.
