The analysis of the propulsion performance considering the ship motion in waves is an important factor for the efficient operation of a ship. The interaction between the propeller and the free surface due to the ship motion in waves has a great influence on the propulsion performance. However, most of recent researches about the hydrodynamic performance of ships in waves focus on the added resistance, and the experimental or numerical data on the propulsion performance considering the ship motion in waves is very rare. In this paper, numerical investigation on the nominal wake in regular head waves is performed for a KVLCC2 model ship at a full-load condition. Phase-averaged and instantaneous wake fields during one period are compared with the experimental data measured by SPIV showing good agreement. And the effect of the ship motion on the characteristics of wake field and the propulsion performance are investigated varying the wave length.
IMO(International Maritime Organization) has established the EEDI (Energy Efficiency Design Index) standard in 2013 and has been strengthening regulations on air pollutants that lower the pollutant emission standards such as SOx in ship fuel from 2020. As such regulations have been strengthened, there has been an increased interest in improving the operational efficiency of ships for fuel saving. As a result, studies on the performance of ships in waves similar to actual marine environments have been concentrated.
Previous studies on resistance and propulsion performance of ships in waves have been performed mainly in terms of added resistance. However, the EEDI formula for improving the operational efficiency of a ship includes weather factors(fw). The weather factor is determined by propeller propulsion performance as well as added resistance (Jung et al., 2017). Therefore, it is essential to analyze the flow phenomenon on the propeller plane in terms of propulsion performance for a successful prediction of the speed performance of a ship operating in waves. In case of ship operating in waves, the variation of dynamic position of the ship by vertical motion is predicted and, especially, the propeller submerged depth changes according to the behavior of the stern part. According to the change of the propeller submergence depth, the interaction between the propeller and free surface can causes some risks, such as air ventilation and surface piercing running (Paik, 2017). Therefore, it is necessary to clarify the flow phenomenon on propeller plane considering the vertical motion of the ship in order that analyze accurately the propulsion performance of the ship.