This paper shows the comparison results of added resistance in waves of a ship obtained from several methods such as NMRI(National Maritime Research Institute)'s formula, small scale model test and a numerical analysis using 3D Rankine panel method. The Marine Environmental Protection Committee (MEPC) of International Maritime Organization (IMO) statutory requires minimum propulsion power so that a ship can maintain its manoeuvrability even in adverse weather conditions. Minimum propulsion power is in general estimated considering resistance in calm sea, wind resistance and added resistance in waves all together. For the prediction of added resistance in waves, as described in ISO 15016, NMRI formula, small scale model test and direct numerical analysis are allowed. From this study, it is found that minimum propulsion power estimated using NMRI formula which is widely accepted and popular in marine industry is significantly conservative compared with that of a small scaled model test which was carried out by a well-known prominent model test basin. It needs to be investigated further but the deviation of NMRI formula appears to be the fact that it might be calibrated normally at design speed, not minimum speed under minimum propulsion power. On the other hand, it is worthwhile to note that numerical analysis using 3D Rankine panel method is very similar to the model test. In conclusion, numerical method such as Rankine source method can be effectively used for optimum sizing of marine engine in terms of minimum propulsion power.
Designing an optimized hull form to improve the operational efficiency is an important objective in the design process. In order to optimize the hull form, it is necessary to estimate the resistance acting on the ship and hull form design has been traditionally performed considering resistance in calm water without the influence of wave and wind. However, for the accurate evaluation of ship performance in the actual operational condition, not only the resistance in calm water but also the added resistance due to waves and winds should be considered and the added resistance in waves is defined as follows: