PROPULSIVE PERFORMANCE OF A CONTAINER SHIP IN WAVES

With a model of single screw high speed container ship, resistance and self-propulsion tests in regular and irregular waves are carried out in the Experimental Tank of Osaka University. The experimental results of ship motion in regular head and following waves and mean increase of resistance in regular head waves are compared with the results obtained from the theoretical calculations. The effects of wave height and propeller diameter on ship motions, mean increases of resistance, propeller thrust, torque and revolutions, self-propulsion factors and propeller load fluctuations are investigated. The significant amplitudes of heave, pitch and the mean increases of resistance, propeller thrust, torque and revolutions measured in irregular waves are compared with the values which are predicted from the response operators obtained from the experiments in regular waves and the wave spectra by applying the linear superpositon method. The self-propulsion factors in regular and irregular head waves are analysed by assuming that the mean characteristics of propeller in waves are identical with those in still water. Furthermore, to investigate the characteristics of self-propulsion factors in waves, the inflow velocity into the propeller disk in regular waves are measured by using a ring type wake-meter, and the wake fraction, relative rotative efficiency and propeller open-water efficiency in regular waves are calculated by using the measured inflow velocity distribution, the propeller revolutions and the propeller open-water characteristics. The measured amplitudes of propeller load fluctuations are compared with the theoretical calculations by using the propeller open-water characteristics in uniform flow.