• Journal of Ocean Engineering and Technology
• /
• v.32 no.6
• /
• pp.419-426
• /
• 2018

Recently, in an effort to reduce the energy efficiency design index (EEDI), studies on energy saving devices (ESDs) have been conducted. In this study, we designed a post-device suitable for a KRISO container ship (KCS) using computational fluid dynamics (CFD). In order to increase the efficiency of the post-device, a twisted rudder was used, which has a proven performance (showing a 1.34% reduction in DHP compared to the bare hull at 24 knots) in previous research at Pusan National University. In addition, an increase in efficiency was expected by the use of a rudder bulb, including the discontinuous section of the twisted rudder and a divergent propeller cap to prevent the contraction of the wake. The optimization criterion was the case where the delivery power was the least compared with the bare hull. We analyzed the cause of the efficiency increase through an analysis of the self-propulsion factor. The case study for optimization was divided into 4 types (1. clearance of the bulb and cap, 2. shape of the bulb, 3. size of the bulb and cap, and 4. asymmetric bulb). Finally, with a clearance of 50 mm from the ship, a spherical bulb with the cap having an angle of $5^{\circ}$, and an asymmetric rudder bulb with a bulb diameter of 1.2HH/1.4H (horizontal/vertical) showed a 2.05% reduction in DHP compared to the bare hull at 24 knots. We will fabricate a post-device that will be optimized in the future and verify the performance of the post-device through model tests.

• Journal of the Society of Naval Architects of Korea
• /
• v.57 no.6
• /
• pp.381-387
• /
• 2020

According to the increase of concern for environmental problems, the energy saving becomes an important issue because it is one of the most effective methods of decreasing CO2 which is major environmental problem. In the present study, the post device after propeller related with rudder has been focussed. Recently the full-spade twisted rudder has been frequently used not only to increase the efficiency but also to remove the cavitation risk on leading edge. In addition to that the rudder bulb is also applied to the rudder to increase the propulsion efficiency as well as to minimize the cavitation erosion risk around twisting part. The parametric study has been conducted for investigating the optimum configuration of twisting rudder with bulb by CFD. The present optimization has been applied to the KVLCC2 full-body ship. The verification of the computed results is also expected to be conducted by the comparison with experimental results in the near future.

• Journal of Advanced Marine Engineering and Technology
• /
• v.39 no.1
• /
• pp.1-7
• /
• 2015

The environmental regulations for CO2 emissions from the ship have been established recently, and fuel oil price has been increased continuously. In order to overcome these circumstances, Energy Saving Devices (ESDs) have been developed continuously to reduce the fuel oil consumption and improve the propulsive efficiency. This paper describes the trial performance of PBCF (Propeller Boss Cap Fins), SCHNEEKLUTH duct, Asymmetric rudder bulb and Mewis duct applied to handy-size bulk carriers. As a result, SCHNEEKLUTH duct is more effective than other energy saving devices at the reducing the fuel oil consumption and the improvement of the propulsive efficiency. In addition, it is confirmed that SCHNEEKLUTH duct is really effective in the vibration of the deck house. And the fuel oil consumption can also be reduced through main engine de-rating.