Study on the rudder characteristics of ultimate rudder by numerical calculation

The authors invented Ultimate Rudder3) as the rudder with bulb. The authors calculated the rudder characteristics of the normal rudder and Ultimate Rudder by CFD at several steering angles and compared these values. The result showed that regardless of the presence or absence of the bulb, signs of separation appear on the control surface with a steering angle of 20 deg. to 30 deg. and regarding the steering torque coefficient, it was found that the steering torque coefficient of Ultimate Rudder is larger than the normal Rudder when the steering angle is less than 20 deg. and also the steering torque coefficient can be decreased by changing the shape of the rudder bulb

Efficiency improvement effect and water noise reduction by energy saving devices

In recent years, the Energy Efficiency Design Index (EEDI) regulations for global GreenHouse Gas (GHG) reduction has been strictly updated. From these back ground, environmentally friendly operation and propulsion systems are expected. In the view of propulsion system design, GHG reduction by improving propulsion efficiency and comfortable habitability by noise reduction are focused. Consequently, many ship designers and manufactures developed a variety of energy saving devices such as the propeller cap with fins, rudder bulb and duct to improve propulsion efficiency. In general, the improvement effects of each energy saving devices are estimated by ship designers or manufactures. Therefore, when several energy saving devices is installed with the ship, several energy saving devices, the actual degree of propulsion efficiency from synergistic effects are sometimes unknown at the design stage. In this paper, in order to evaluate synergistic effects of energy saving devices, the authors designed ECO-Cap[1], Ultimate Rudder Bulb[2] and Neighbor Duct[3] for 82kBC by using CFD and then conducted the model tests of each devices. Furthermore, the combinations tests of such devices were carried out in model tests. This paper summarizes the synergistic effects of energy saving devices on the basis of the model tests. In addition, noise reduction effects by energy saving devices are also described for informative reference