Performance Analysis of Single-propeller/Twin-rudder System by Computational Fluid Dynamics

摘要

The single-propeller/twin-rudder system composed of single propeller and two high-lift rudders of fish-tail type has been installed on 60 vessels in Japan. With this system, a ship can be maneuvered at any mode including going astern, hovering, dead slow forwarding and turning by means of various rudder angle combination, with propeller revolution being kept in the forward direction. Using a single joystick lever, it is possible to give the required position of each rudder and to develop thrust in all directions. The system has been installed on relatively small size vessels which require easy and short time approaching to and from berth. Studying work has been continued to apply the system to medium size vessels and some of the results are presented in this paper. Geometrical forms of rudder such as blade thickness ratio and shape of rudder section play important roles for the drag characteristics of the rudder. Effect of the thickness ratio and variation of shape of ruder section to the drag is studied by computational fluid dynamics. To improve propulsive efficiency of the twin rudder system, a pair of reaction fins is attached between two rudders where the propeller slip stream passes. Form of the fin affects propulsive performance a great deal and some results are discussed together with experimental results.