Dae-Won Seo

A Proposal on Standard Rudder Device Design Procedure by Investigation of Rudder Design Process at Major Korean Shipyards

Recently, a very large vessels maneuvering performance, rudder performance and rudder designs importance are considered to be an important subject. However, there have been few studies on the design process of rudder device before. The aim of this paper is to investigate a design process of rudder device and to propose a generalized design process of rudder device. Firstly, we investigated the rudder device design process of Korean major shipyards. And the differences of a torque calculation method, rudder section design, maneuvering performance examination method, etc. were analyzed theoretically. Secondly, the design process of rudder device was divided into concept design, initial design and detail design, rudder profile and design method have been selected through rudder form determination process. And principal dimension and steering gear capacity were determined. Maneuvering performance was also examined by simulation tool. In detail design, design criteria which had been considered in rudder initial design was investigated thoroughly. Also a rudder torque, rudder cavitation performance and rudder structure analysis were estimated. And maneuvering performance was also examined by model test. Finally, based on the results of investigation, the design process of rudder device was generalized and proposed.

Influence of Jet Nozzle Arrangement on the Performance of a Coanda Foil

The Coanda effects demonstrate that a jet stream applied tangential to a curved surface can generate lift force by increasing the circulation. Many experimental and numerical studies have been performed on the Coanda effect and it is found to be useful in various fields of aerodynamics. The Coanda effect may have practical application to marine hydrodynamics since various control surfaces are being used to control behaviors of ships and offshore structures. In the present study, numerical computations are performed to find the applicability of the Coanda effect to the marine control surfaces. For the purpose, changes in flow characteristics around a flapped foil due to the Coanda effect have been simulated by RANS equations discretized with a cell-centered finite volume method (FVM). In the process, special attention has been given to the influence of jet nozzle arrangement on the lift characteristics of the Coanda foil. It is found that the shape as well as the location of the jet intake and jet exit affects the lift performance of the foil significantly.

A Study for Improvement of Lift Performance of a Horn-type Rudder with the Coanda Effect

The Coanda effect is noticeable when a jet stream is applied tangential to a curved surface since then the jet stream remains attached to the surface beyond the point where flow separates otherwise and results in augmentation of circulation and lift. Numerous experimental and numerical studies have been performed in various fields of aerodynamics to exploit the Coanda effect and many of them found to be useful. It can be speculated that the Coanda effect may have practical application to the field of marine hydrodynamics as well since various control surfaces are being used to control behaviors of ships and offshore structures. In the present study, the Coanda effect has been applied to a horn type rudder and a series of numerical computations and model experiments are performed to find the practical applicability. The results indicate that the Coan da jet increases the lift coefficient of the rudder as much as 52% at the momentum coefficient Cj = 0.1 and the rudder angle α = 10°.

On the Influence of End Plates upon the Tip Vortex Cavitation Characteristics of a Fin Stabilizer

AbstractFins are widely used for roll stabilization of passenger ferries and high performance naval ships, among others. In the present study, numerical simulation s are performed to investigate the influence of end-plates upon the cavitation cha racteristics of a stabilizer fin for various angles of attack and speeds and the results are ver ified through a series of model experiments. It is found that a considerable retardation in tip vortex cavitation can be achieved with attachment of end-plates at the tip of the sta bilizer fin. The results can be utilized for the design of stabilizer fins as well as the development of high performance control devices for ships. ※Keywords: Cavitation(공동현상), Stabilizer fin(안정기 핀), End-plate(날개 끝판), NACA 0015, Model experiment (모형시험), Numerical simulation(수치해석) 1. 서론 최근 선박의 대형화, 고속화 추세에 따라 프로펠러, 타, 안정기 용 핀 등에서 공동현상이 자주 발생하고 있다. 날개 주위로 유입된 물이 흡입면을 지날 때 증기압보다 낮은 압력영역에서 형성된공동은 압력이 증기압보다 높은 영역에 이르면 접수일: 2007년 8월 23일, 승인일: 2008년 2월 3일✝교신저자, shlee@inha.ac.kr, 032-860-7337

Numerical Study on the Gap Flow of a Rudder System with Bisymmetric Blocking Bar

AbstractIn recent practice a half round prismatic bar has fillet welded or formed through foundry work along the centerline on rear concave surface of the horn to mitigate gap flow between fixed and movable part of the rudder system. When the gap clear ance has been blocked with this practice, numerical simulations indicate that the pra ctices are not only effective in reducing the gap flow but also in mitigating the cavitation. Th e blocking effects are remarkably improved when a pair of blocking bar is bisymmetrica lly attached with respect to centerline on the opposite convex surface of the movable part. The blocking bar could be placed on the exposed surface under maximum rudder angle. This implies that the blocking bar could be easily adopted not only in a design stage but also in a maintenance stage for mitigating rudder cavitation. In addition, the numerical simulations imply that more improvements could be anticipated through the selection of sect ion shape of prismatic bar for gap flow blocking.

A Numerical Study for Design of a Fixed Type Fin Stabilizer Utilizing the Coanda Effect

Fins are widely used for roll stabilization of passenger ferries and high performance naval ships, among others. The Coanda effect is noticeable when a jet stream is applied tangentially to a curved wing surface since the jet can augment the lift by increasing the circulation. The Coanda effect has been found useful in various fields of aerodynamics and speculated to have practical applicability in marine hydrodynamics where various control surfaces are used to control motions of ships and the other offshore structures. In the present study, numerical computations have been performed to find proper jet momentum coefficients and trailing edge shapes suitable for the application of the Coanda effect to a stabilizer fin. The results show that the lift coefficient of the modified Coanda fin at the zero angle of attack identically coincides with that of the original fin at

A Numerical Study on the Control of the Gap Flow Using a Fluid Supply Device

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A Study to Improve the Lift Performance of a Full Spade Rudder with the Coanda Effect

AbstractRecently, horn-type rudders are generally being used at high speed container ships and are frequently suffering from the cavitation occurs on the rudder surface in the vicinity of the gap between the horn and rudder plate. In the present study, a fluid supplying device is employed as to decrease the gap cavitation of the horn-type rudder. The device is devised to inject the water against the pressure side through the nozzle installed inside of the gap to control the gap flow. Numerical calculations are performed to investigate the effectiveness of the device and the results show that the device can noticeably reduce the gap cavitation. The rates of water injection for achievement of the maximum retardations of gap flow are also sought. ※Keywords: Horn-type rudder(혼타), Gap flow control(간극 유동제어), Cavitation(공동현상), Fluid supplying device(유체 공급 장치), Numerical Simulation(수치해석) 1. 서론 최근 선박의 대형화 및 고속화 추세에 따라 프로펠러, 타, 안정기용 핀 등에서 공동현상이 자주 발생하고 있다. 이러한 공동현상은 날개 주위로흐르는 물이 흡입면을 지날 때 증기압보다 낮은

Recent Development in Technologies for Short Sea Shipping and its Implications

The shape of a conventional full spade rudder has been modified to implement the Coanda effect and consequential changes in the flow characteristics are carefully examined to show the significant enhancement in the lift performance. A preliminary numerical study has been done to identify the optimum configuration of the modified rudder sections. For the purpose, chord wise locations of the jet slit and the radii of the trailing edge were varied in several ways and the changes in the lift characteristics have been observed at the various angles of attack, particularly focusing on the usefulness of the Coanda effect upon delaying the stall or increase in the circulation. Making the most use of the results so attained, full spade rudder of a VLCC has been reformed to realize the Coanda effect. A series of model experiments and numerical simulations are performed to confirm the effectiveness of the Coanda effect in improving the performance of the modified rudder. It is found that considerable enhancement in the lift performance of the rudder is plausible at any rudder angle if an optimum jet momentum is provided.

Technical Implication of an Intermodal Transport System for Implementation between Korea and China - On a train ferry system for Incheon harbor -

Recently, the logistics industry in Asia is growing rapidly mostly with Chinese economic development. A variety of studies have been carried out to reduce the logistic cost under the situation that the global freight traffic continues to increasing. The Short Sea Shipping(SSS) system, a multi modal transport system centered around coastal shipping to realize high value-added logistics, achieved considerable success in EU. To implement the SSS system in Korea, it is necessary to develop the various essential technologies related to development of efficient ships and port facilities, including equipment for loading and unloading containers, operating and managing systems for freight terminals and technologies for tracking and securing containers. The present paper focuses on the survey of the current essential technologies available for implementation of the SSS system and suggests the direction of future development in the technologies.