Isao Funeno

Design system for optimum contra-rotating propellers

A new type of contrarotating propeller (CRP) system has been developed through the cooperative research work of five shipbuilding companies in Japan (Hitachi Zosen Corporation; Kawasaki Heavy Industries, Ltd.; Mitsui Engineering and Shipbuilding Co., Ltd.; NKK Corporation; and Sumitomo Heavy Industries, Ltd.). This paper describes a design system for an optimum CRP, which is one of the numerous outcomes of this work. The optimum design system is composed of three theoretical programs: (1) the design program of the optimum CRP; (2) the steady lifting surface program of the CRP; (3) the unsteady lifting surface program of the CRP. These theoretical programs will be discussed in the first part of the paper, and the design system supported by these theoretical programs will then be verified by comparing calculated and experimental results.

On Scale Effect of the Resistance due to Stern Waves Including Forward-oriented Wave Breaking just behind a Transom Stern

This paper describes how when a ship with a wide immersed transom stern operates on a deeper draft, forward-oriented wave breaking often occurs just behind the transom stern. Stern waves in such conditions consist of two main components: the forward-oriented wave breaking and remained following waves. The purpose of this paper is to develop a method to treat the remained following waves and to clarify scale effect of such stern waves. Methods have been developed to estimate resistance. Most of the recent container ships have wide immersed transom sterns to keep necessary stability with much more containers on deck as compared with ships of two decades ago. When such a ship runs on a deeper draft than its design draft, forward-oriented wave breaking with high turbulence intensity occurs just behind the transom stern. The phenomenon accompanies large momentum loss and accordingly generates large hull resistance. Research is important for energy saving for such ships.