• 한국항해학회지
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• 제10권2호
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• pp.97-114
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• 1986

Ship's maneuverability is very important factor in safe ship handling and economical ship operation. Steering characteristics are consisted of course stability and maneuverability. Today in many advanced ship-building countries, they study ship's course stability, using model ship tests, such as straight line tests, rotating arm tests and Planar Motion Mechanism (PMM) etc., in tow in tanks. It is the purpose of this paper to provide ship's handlers with better understanding of steering characteristics and to help them in safe controlling and manevering . In this paper, the author simulated response of various vessels, running straight course with constant speed, and they are disturbed by small external disturbance of one degree yaw angle with no angular velocity . The author used the hydrodynamic derivtives resulted at tests of Davidson's laboratory in Stevens Institute of Technology, New Jersey, U.S.A. Course stability was evaluated and analyzed in various respects, such as block coefficient, ratio of ship's length to beam, draft and rudder area ratio etc. The obtained results are as follows : (1) The ship's course stability is affected by magnitude of block coefficient greatly. In case that the block coefficient is more than 0.7, the deviation varies at nearly same rate but the requistite time to reach the steady course is different. (2) The ship's course stability is affected by magnitude of L/B. When the dimensionless time reaches about 3, the deviation and requisite time to reach the steady course are influenced nearly same. After the dimensionless time is about 3, they change on invariable ratio. (3) The effect to course stability by L/T and RA' can be neglected. (4) The reason why thy VLCC and container feeder vessel are unstable on their course is that their block coefficient is generally more than 0.8 and the ratio of ship's length to beam is about 6.0.

• International Journal of Naval Architecture and Ocean Engineering
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• 제13권1호
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• pp.585-598
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• 2021

The course-keeping stability of a high speed planing boat should be considered at the design stage for its safe operations. The shape of waterjet intake plane is one of important design parameters of a waterjet propelled planing boat. That has significant influences on the stern flow patterns and pressure distributions. In this study, the effects of the waterjet intake shapes of planing boats on the course-keeping stabilities are investigated. Two kinds of designed planing boats have the same dimensions, but there are differences in waterjet intake plane shapes. Captive and free-running model tests, Computational Fluid Dynamics (CFD) analyses are carried out in order to estimate their hydrodynamic performances including course-keeping stabilities. The results show that the flat and wide waterjet intake plane of the initially designed boat makes the course-keeping stability worse. The waterjet intake shape is redesigned to improve the course-keeping stability. The improved performances are confirmed by free-running model tests and full-scale trials.

• 대한조선학회논문집
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• 제37권2호
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• pp.46-56
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• 2000

본 논문은 손상선박의 안전대책에 관한 연구의 일환으로, 황천항행중인 선박이 충돌, 좌초 등 원인에 의해 손상을 받았을 때를 가상하고, 손상선박을 다른 안전한 장소로 예항하고자 할 때의 침로안정성 문제를 다루고 있다. 외력으로는 바람의 영향만을 고려할 때, 예선 피예선계의 침로안정성 평가를 위한 특성방정식을 도출하고, 피예선의 각 손상상태에 따른 침로안정성을 수치계산하였다. 그 결과 손상상태, 풍속, 풍향 및 예항삭의 길이 등이 침로안정성에 미치는 영향을 평가할 수 있었다.

• 대한조선학회논문집
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• 제33권4호
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• pp.1-14
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• 1996

IMO 조종성잠정기준 4가지 항목중, 특히 비대선형의 경우 침로안정성이 문제시될 수 있다. 본 연구의 목적은 타의 스팬길이에 따른 면적 변화가 침로안정성에 미치는 영향을 조사함으로써, 타면적 증감에 의한 침로안정성 개선 방법을 모색하고자 한다. 본 연구에서는 타직압력과 관련된 실험 정수들과 조종유체력미계수와의 관계를 정식화하였고, 타직압력과 관련된 각종 구속모형시험을 실시하여 타면적 변화에 따른 조정유체력미계수의 변화를 구하고, 이로부터 침로안정성을 비교, 분석하였다. 또한 조종성 시뮬레이션 기법을 이용하여 타면적 증감에 따른 조종성능 개선 효과를 검토하였다. 연구 결과, 타면적 증가는 침로안정성을 저해할 가능성이 있으며, 그 원인은 스팬길이 증가로 인한 타 상부와 선미 오버행 하부의 공간이 작아지기 때문이다. 이 공간은 조종운동시정류계수에 큰 영향을 미치며, 이것이 침로안정성과 관련된다는 것을 알 수 있었다.

• 대한조선학회논문집
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• 제45권5호
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• pp.523-529
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• 2008

The course stability performance for tankers is evaluated by computational fluid dynamics. In the present work, a Reynolds averaged Navier-Stokes (RANS) code is applied to a maneuvering problem covering the pure drift and yaw motions. The purposes of this study are to evaluate the hydrodynamic force in the bare hull (AFRAMAX) in pure drift and yaw motion and to provide information about the trends in the forces and moments when the rudder angles are varied. The flow simulation is performed by FLUENT. The CFD code is examined to find the optimistic computational condition such as size of grid, turbulence model and initial condition. The hydrodynamic derivatives in drift and pure yaw motion are estimated by the numerical simulation, and then the stability levers are calculated. It is confirmed that the computations show the superiority and inferiority of course stability performance according to the hull forms. Finally, the CFD code is applied to the estimation of the rudder forces when the rudder angles are varied. The propeller effect expressed by the body force distribution is also included.

• 한국실내디자인학회논문집
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• 제20호
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• pp.3-9
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• 1999

The purpose of this study was to verify the stability of environmental disposition through analyzing the short term effect of the 'Interior Design History' course on students environmental dispositions, especially their interior image preferences toward traditional/modern, female/masculine, and simple/complex characteristics. The pre-test post-test control group experimental design was used. The independent variable was the experience of the Interior Design History course, and the dependent variable was environmental disposition measured by IIPS(Interior Image Preference Scale). The measurements were done at both beginning and end of fall semester, 1997. Subjects were using 71 undergraduate students of Drafting course (control group) and 35 undergraduate students of Interior Design History course (experimental group) at Y University. Data were analyzed using frequency, percentage, mean, and F-test through ANOCOVA. This research revealed no effect of the Interior Design History course on students interior environmental dispositions. The stability of those environmental dispositions and also the validity of the IIPS were proved.

• 한국해양공학회지
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• 제11권3호
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• pp.100-106
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• 1997

Despite various devices have been developed and applied to stabilize the yaw motion, the superiority of twin skeg over other equi-functioned appendages has been recognized so far. In many cases, these skegs were installed with insufficient study and analysis for design, and this leads to the worse performance of their resistance and course keeping than required. Experimental studies on the effect of various kinds of anti-yawing skegs to the course keeping stability and on the additional resistance caused by them were carried out in the circulating water channel(CWC) at Chosun University(CU). Course keeping stability tests for four different size of skegs, resistance tests for three different shapes of skeg(including deformed skegs) were performed systematically. And the effect of angle of skegs on resistance was studied at the final stage.

• International Journal of Naval Architecture and Ocean Engineering
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• 제13권1호
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• pp.12-23
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• 2021

In the conventional experiment to assess the towing operations, the towing stability of the towed vessel has been evaluated under the condition without lateral motion of the tug-boat. However, the tug-boats may have a lateral force to change the direction of the towed vessel. In this study, experiments have been conducted considering unsteady conditions in the towing system. First, a towing test system in a Circular Water Channel (CWC) using the conventional experimental method is built. Second, the towing characteristics of the towed vessel are investigated using the conventional method, and they are compared with other research results and stability discriminant criteria. Third, the lateral motion of the tug-boat was modeled as a sinusoidal motion using a forced oscillation device changing frequency and amplitude. Finally, the discussion is given in terms of both towing- and course-stability of the towed vessel according to the lateral motion of the tug-boat.

• 해양환경안전학회지
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• 제24권4호
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• pp.430-437
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• 2018

파랑중을 항행하는 선박에는 저항증가와 함께 파랑에 의한 횡력 및 회두모멘트가 정수중과 다르게 작용하여 선박의 조종성능에 영향을 미치게 된다. 따라서 파랑에 의해 발생하는 횡력 및 회두모멘트를 추정하는 것이 중요하므로 본 연구에서는 이와 같은 문제를 해결할 수 있는 수치계산을 이행하였다. 본 연구에서는 CFD를 이용하여 정수중 및 파랑중에서 부선에 작용하는 유체력 계산을 위한 수치시뮬레이션을 수행하였으며, 이 결과를 토대로 최종적으로 파랑중 부선의 침로안정성 특성에 대하여 조사 및 분석하였다. 정수중보다는 파랑중에서 부선에 작용하는 유체력이 강해지고 있으며, 파랑중에서도 파장이 길어질수록 유체력이 커지고 있는 모습을 확인할 수 있다. 장파장 영역에서는 yaw damping lever의 (-) 값이 정수중보다 커지고 있으나, 단파장 영역과 파장이 선박길이와 일치하는 영역에서는 각각 작아지고 있어서 이 영역에서는 침로안정성이 향상되고 있다고 추정할 수 있다. 즉 장파장 영역에서는 침로안정성이 정수중 및 단파장 영역보다 상대적으로 나빠지고 있으므로 항행시 주의가 필요하다고 할 수 있다.

• 대한조선학회논문집
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• 제34권3호
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• pp.27-37
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• 1997

본 연구는 특수타의 채택으로 인한 침로 안정성 개선 효과에 관한 내용을 담고 있다. 구체적으로 여러 특수 형태의 타(본 연구에서는 특수타로서 볼록타, 오목타, 플랩타, 엔드플레이트타를 생각함)를 동일 선체에 설치하였을 때의 침로 안정성 개선 효과를 조사하기 위해서, 먼저 특수타의 타 단독 시험을 실시하여 양력 개선 효과를 조사하였으며, 또한 선체-프로펠러-타 시스템에서의 각종 구속 모형 시험을 실시하여, 특수타가 타수직력과 관련된 실험 정수들에 미치는 영향을 조사하였다. 그리고 실험 결과로부터 특수타의 채택에 따른 조종성 미계수의 변화를 구하고, 침로 안정성을 정량적으로 분석, 비교 및 검토하였다. 그 결과, 볼록타와 오목타 그라고 플랩타는 침로 안정화에 거의 기여하지 못하고, 엔드플레이트타는 침로 안정성을 크게 향상시킨다는 것을 확인하였다. 본 연구 결과는 초기 설계 단계 또는 선박 건조 후 침로 안정성이 문제시된 선박에, 선미 형상의 설계 변경없이 타의 형상 개조만으로 침로 안정성을 개선시키고자 할 때 유용하게 활용될 것으로 기대된다.