• Journal of the Society of Naval Architects of Korea
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• v.35 no.1
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• pp.46-53
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• 1998

In this paper, we studied to improve Inoue's[1] and Kijima's[2] model used to predict ship's manoeuvrability at initial design state. To perform this work, we carried out PMM(Planar motion Mechanism) test and rudder open water test for 12 models of low-speed blunt-ship which have horn type rudders and bulbs in afterbody. As we adopted MMG(Mathematical Modelling Group) model, we could analyze hydrodynamic and MMG experimental coefficients. The regression analyses by principle parameters were carried out for hydrodynamic and MMG experimental coefficients. The regression analyses by principle parameters were carried out for hydrodynamic and MMG experimental coefficients and the equations by regression analysis wee used to search sensitivities and to estimate ship's manoeuvrability. We had simulated ship's manoeuvrability to check revised MMG.

• Journal of Ocean Engineering and Technology
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• v.32 no.5
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• pp.386-392
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• 2018

It is necessary to predict hydrodynamic derivatives when assessing the maneuverability of a submarine. The force and moment acting on the vehicle may affect its motion in various modes. Conventionally, the derivatives are determined by performing captive model tests in a towing tank or applying a system identification method to the free running model test. However, a computational fluid dynamics (CFD) method has also become a possible tool to predict the hydrodynamics. In this study, virtual captive model tests for a full-scale submarine were conducted by utilizing a Reynolds-averaged Navier-Stokes solver in ANSYS FLUENT version 18.2. The simulations were carried out at design speed for various modes of motion such as straight forward, drift, angle of attack, deflection of the rudder, circular, and combined motion. The hydrodynamic force and moment acting on the submarine appended rudders and stern stabilizers were then obtained. Finally, hydrodynamic derivatives were determined, and these could be used for evaluating the maneuvering characteristics of the submarine in a further study.

• Journal of Power System Engineering
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• v.10 no.1
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• pp.96-101
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• 2006

In ship operation the consequence of roll and pitchingmotion can seriously degrade the performance of mechanical and personnel effectiveness. So many studies for the roll stabilization and trimming control system design have been performed and good results have been achieved where the stabilizing fins, tanks, rudders and flaps are used. However the ultimate objective of such approach should be focused on improving the boarding sensitivity. But there may exist many unsolved problems, for examples, ship control performance degradation and increasing of system complexity. So, the achieved control performance could not give us enough comfortable boarding sensitivity where the residual rolling and pitching motion are main drawbacks. To get rid of these disadvantages, the main hull control systems design approach has been considered using semiactive absorber. In this system, dampers, spring, dynamic dampers and control system with sensors are incorporated. In our system considered in this study, just two motors and control system with sensors are used for the bed. And the control system can be installed on each bed. So, we can control every bed on the specified control objective respectively. Above all, the good advantages of this system are the facts followed from simple idea and usefulness. Of course the structural modifications are needed. Considering disturbances, we design control system and verify the usefulness of developed system from the experimental study.

• Journal of the Society of Naval Architects of Korea
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• v.46 no.6
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• pp.578-586
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• 2009

Recently, 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.

• International Journal of Naval Architecture and Ocean Engineering
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• v.12 no.1
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• pp.943-956
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• 2020

In this study, the motion control problem of the vessel towed by a towing ship (tugboat) is considered. The non-powered towed ship is dragged by the towing ship. Even though the towed ship is equipped with propulsion systems, they cannot be used at low or constant speeds due to safety issues. In narrow canals, rivers, and busy harbor areas especially, where extreme tension is required during towing operation, the course stability of the towed vessel depends on the towing ship. Therefore, the authors propose a new control strategy in which the rudder system of the towed vessel is activated to provide its maneuverability. Based on the leader-follower system configuration, a nonlinear mathematical model is derived and a back-stepping control is designed. By simulation and experiment results with a comparison study, the usefulness and effectiveness of the proposed strategy are validated.

• Journal of Ocean Engineering and Technology
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• v.37 no.4
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• pp.129-136
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• 2023

To evaluate manoeuvring performance of merchant ships, the mathematical modeling group (MMG) or computational fluid dynamics (CFD) simulations are used. However, it is difficult to use the MMG to evaluate the manoeuvring performance of fishing vessels, thus research using CFD simulations is necessary. Also, since the course-changing and turning ability is crucial in fishing operations, a rudder design suitable for fishing vessels is necessary. This study designs a rudder using National Advisory Committee for Aeronautics (NACA) airfoil sections and evaluates its manoeuvring performance. A CFD model is used to evaluate the manoeuvring performance of the fishing vessel, and turning and zig-zag tests are conducted. The effectiveness of using CFD simulations based on Reynolds averaged Navier-Stokes equations to assess the manoeuvring performance of fishing vessels was validated. No significant difference was found in the manoeuvring performance for hull forms and rudder designs for course-changing ability. However, the original hull form showed superior turning performance. Among five rudders with varying aspect ratios and shapes, the rudder with 5.5% aspect ratio had the best turning performance. Regarding the rudder design for fishing vessels, NACA airfoil was employed, and a rudder aspect ratio of 5.5% based on the immersed hull side area is recommended.

• Elastomers and Composites
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• v.35 no.1
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• pp.38-45
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• 2000

Influence of rubber composition on migration of antiozonants to the surface in ternary rubber-based vulcanizates composed of natural rubber (NR) styrene-butadiene rubber (SBR), and butadiene rubber (BR) was studied. Of the three rubbers, contents of two rudders were same and only the other one content was different (variable rubber) IPPD and HPPD were employed as antiozonants. Migration experiments were performed at $60^{\circ}C$ for 21 days and outdoors for 4 months. Migration rates of the antiozonants increase by increasing the content ratio of the variable rubber in the vulcanizares from NR/SBR/BR=1/1/0.2 to 1/1/1 and then decrease with an increase of the content ratio of the variable rudder from 1/1/1 to 1/1/5. Migration behaviors of the antiozonants in the ternary rudder-based vulcanizates depending on the rubber composition were explained by the intermolecular interactions between rubber and antiozonant, by the solubility difference of the antiozonants for the rubbers, and by the interface formed between dissimilar rubbers in the triblends.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.5
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• pp.335-342
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• 2020

Tailless aircraft designed for stealth efficiency uses spoilers instead of rudders for the directional control. When the spoiler is rapidly deployed, highly nonlinear and unsteady aerodynamic characteristics can be generated, resulting in adverse effects on aircraft flight performance. This paper investigates the aerodynamic characteristics of an airfoil with moving spoiler using dynamic mesh CFD technique. The effects of spoiler operation speed, mounting location, and deployment scheduling are analyzed to reduce the adverse effects of the spoiler's dynamic operation. The results shows that the adverse effects of dynamic spoiler can be reduced by appropriate selection of the spoiler mounting location and deployment scheduling.

• Journal of the Society of Naval Architects of Korea
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• v.54 no.1
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• pp.18-25
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• 2017

This study deals with numerically comparing performance according to rudder shape called 'Twisted rudder and Wavy twisted rudder'. In comparison with conventional rudder, rudder with wavy shape has showed a better performance at high angles of attack($30^{\circ}{\sim}40^{\circ}$) due to delaying stall. But most of study concerned with wavy shape had been performed in uniform flow condition. In order to identify the characteristics behind a rotating propeller, the present study numerically carries out an analysis of resistance and self-propulsion for KCS with twisted rudder and wavy twisted rudder. The turbulence closure model, Realizable $k-{\epsilon}$, is employed to simulate three-dimensional unsteady incompressible viscous turbulent and separation flow around the rudder. The simulation of self-propulsion analysis is performed in two step, because of finding optimization case of wavy shape. The first step presents there are little difference between twisted rudder and case of H_0.65 wavy twisted rudder in delivered power. So two kind of rudders are employed from first step to compare lift-to-drag ratio and torque at high angles of attack. Consequently, the wavy twisted rudder is presented as a possible way of delaying stall, allowing a rudder to have a better performance containing superior lift-to-drag ratio and torque than twisted rudder at high angles of attack. Also, as we indicate the flow visualization, check the quantity of separation flow around the rudder.

• Journal of Institute of Control, Robotics and Systems
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• v.8 no.5
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• pp.363-372
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• 2002

In ship operation, the roll motions can seriously degrade the performance of mechanical and personnel effectiveness. So many studies for the roll stabilization system design have been performed and good results have been achieved. In many studies, the stabilizing fins are used. Recently rudders, which have been extensively modified, have been used exclusively to stabilize the roll. But, in the roll stabilization control system, the control performance is very sensitive to the ship speed. So, we can see that it is important to consider the ship speed in the rudder roll control system design. The gain-scheduling control technique is very useful in the control problem incorporating time varying parameters which can be measured in real time. Based on this fact, in this paper we examine the;$H_{\infty}$-Gain Scheduling control design technique. Therefore, we assume that a parameter, the ship speed which can be estimated in real time, is varying and apply the gain-scheduling control technique to design the course keeping and anti-rolling control system far a ship. In this control system, the controller dynamics is adjusted in real-time according to time-varying plant parameters. The simulation result shows that the proposed control strategy is shown to be useful for cases when the ship speed is varying and robust to disturbances like wind and wave.