Developing Expression Method of Ship Hull Forms and Improvement of Ship Performance in Waves

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We have performed the Research Project titled "Developing Expression Method of Ship Hull Forms and Improvement of Ship Performance in Waves" for two years (1999-2000). The main conclusions obtained in this study are summarized as follows :(1) We make clear that the parameters which strongly affected the seakeeping qualities of ship in waves are the vertical prismatic coefficients of the fore and the aft half body and the water plane area coefficient of the fore half body.(2) It is necessary to take into account the lines fairing of a ship hull form to estimate accurately the effect of bow form and the nonlinear steady disturbance. Therefore, we have investigate the method to describe the lines of the ship hull form by using the B-spline function.(3) We have examined the validity of the existing theories estimating the seakeeping qualities of a high-speed vessel. Strip theory is valid for ship speed less than Fn=0.4. High-speed slender-body theory is the most useful method for estimatio … More n of seakeeping qualities of high-speed vessel. The results of Rankine panel method are much improved by dealing with the transom stern as the dry surface. However, it is not enough for accurate estimation of radiation forces.(4) The differences of estimation accuracies due to 3-D estimation theories are small with respect to a fine conventional ship. However, the steady disturbance due to a bow strongly affects the unsteady wave field. Thereby, the Rankine panel method is recommended for estimation of seakeeping qualities because it can easily take into account the effect of steady disturbance.(5) We have developed the estimation method of unsteady forces that takes into account the effect of nonlinear steady disturbance, and have confirmed that it is more accurate method than the existing methods by comparing with the experimental results.(6) The estimation methods in frequency domain are not enough for estimating the nonlinear hydrodynamic forces depending on a time. Therefore, we have tried to develop the estimation method in time domain for developing the excellent ship hull form. At present, we can get the same accurate results as the existing method by using the newly developed method for a fine conventional ship. Less