Study on the Power Increase in Waves of a Cruise Ship with Podded Propulsion

Abstract

Ship design is evolving towards more cost-effective and greener solutions. In order to design more energy-efficient ships, it is helpful to consider the ship’s propulsion performance not only in still water but also in waves during design optimization. However, the dynamics of the propulsion system in the presence of waves is very complicated and yet to be fully understood. The difficulty is further increased when podded propulsion is the used rather than the conventional propeller-rudder combination. This paper studies the propulsion performance of a cruise ship with podded propulsion in waves based on model experiment. The test data are post-processed by Torque and Revolution Method (QNM), Thrust and Revolution Method (TNM), and Resistance and Thrust Identity Method (RTIM) according to ITTC recommended procedures. The result from the three methods are compared and analyzed, and some recommendations are made. It is found that QNM can provide the most reliable prediction result of power increase in waves, while TNM and RTIM can also produce reasonable prediction result only if the correct propulsive coefficients, i.e. wake fraction and thrust deduction coefficient, are available.