• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• 2015.07a
• /
• pp.11-12
• /
• 2015

두 선박이 정면에서 마주치며 선박간 상호 통항하거나 상대선을 추월할 경우 각 선박의 선체형상과 선속에 의한 유체력 상호작용에 따른 선박간 간섭력이 발생한다. 선박간 간섭력의 주요한 평가 요소인 횡력과 회두 모멘트의 측정을 통해 두 선박이 근접하였을 때의 위험도와 충돌을 예측할 수 있다. 선행된 간섭력에 관한 연구는 대부분 경험에 의하거나 이론적인 측면에서 관련 연구가 진행되어왔으며, 학계에서 통상적으로 널리 알려진 뉴턴의 연구(1960)에서는 깊은 수심에서 두 선박을 평행하게 항주시켰을 때 선박간 최대 흡인력은 두 선박이 정횡으로 나란하게 위치되는 지점에서 발생하고, 이때의 간섭력은 선속의 제곱에 비례한다고 추정하였다. 현대의 조선기술이 발전함에 따라 선박의 크기는 점점 대형화되고 선박의 운항 효율성 증진을 위한 다양한 선형이 개발되어 실선에 적용되고 있다. 이런 경향에 따라 과거에 비해 현대 선박 운항환경에서의 선박간 간섭은 선박의 크기 및 선형에 의한 영향이 클 것으로 판단된다. 본 연구에서는 선박의 종류별로 대표 선종을 선정하여 두 선박이 정면에서 마주치며 통과하는 운항조건에서의 선속 증가에 따른 선박 상호간 간섭력의 변화를 통상적으로 사용되는 선박조종시뮬레이터를 이용하여 실험 및 분석하여 상관관계를 도출하였다. 선박 유형에 따른 시뮬레이션 실험 결과 최대 횡력은 주로 선미 부근에서 발생하였고 최대 회두모멘트는 선수가 근접할 때 발생하였으며, 선속이 증가할수록 선박 상호간 근접거리가 좁혀졌고 선형별로 각기 다른 선속에서 선미 충돌이 발생하였다. 이 실험연구는 선형에 따른 선박 상호간 근접 시의 횡거리와 통과속력에 대한 기준 설정의 연구 근간을 마련하였고 선박간 교항시 안전운항을 위한 지침이 될 것으로 판단된다.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.41 no.2
• /
• pp.156-164
• /
• 2005

The size of the ship's turning circle is influenced by various factors, such as block coefficient, underwater side shape, rudder area ratio, draft, trim and Froude's number. Most of them are already fixed on departure from a port. However, the ship's speed and the rudder angle are controllable factors which operations are able to change optionally during sailing. The DGPS measured the turning circles according to the ship's speed and the rudder angle. The maximum advances by slow and full ahead were 302m and 311m, and the maximum transfers were 460m and 452m, respectively. There occurs almost no difference in size of the turning circle by variation of the ship's speeds. When the rudder angles were changed to $10^{\circ}$, $20^{\circ}$ and $30^{\circ}$, the maximum advances were 447m, 271m and 202m, and then also the maximum transfers 657m, 426m and 285m, respectively. The diameter of the tuning circle was decreased exponentially when the rudder angle was increased. The maneuverability was better when the direction of turning and propulsion of propeller are in the opposite direction rather than in the same one togetherm. The distance of the maximum transfer was always bigger than that of the maximum advance.

• Proceedings of KOSOMES biannual meeting
• /
• 2004.05b
• /
• pp.121-125
• /
• 2004

Recently, High Tensile Steel is adapt to thin plate on the steel structure and marine structure is used widely, It is possible for buckling happens great. Specially, Initial deflection of ship structure happens in place absence necessarily by heat processing of welding or cutting etc. This Initial Deflection is exerted negative impact when thin plate absence complicated nonlinear behaviour accompanied secondary budding. As a result, must idealize initial deflection that occurrence is possible to endow stability and accuracy in the hull structure or marine structure and reflect in early structure design considering secondary buckling. Longi direction of compressive load interacts and analyzed finite element series analysis that apply various kinds initial deflection shape measured actually on occasion that is arranged simply supported condition in this research. Applied ANSYS (elasto-plasticity large deformation finite element method) to be mediocrity finite element program for analysis method and analysis control used in Newton-Raphson method & Arc-length method.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.20 no.2
• /
• pp.96-104
• /
• 1984

This paper is on the prediction and response of the ship hull girder due to slamming of foreward flat bottom plate. The response with respect to foreward flat bottom is divided two kinds by estimating method. One is the estimation of impact forces by slamming, Another is the response of hull girder due to impact forces, that is, displacement, velocity, acceleration, etc. must calculate the values for considered ship hull girder. In this paper, therefore, was estimated only impact forces along ship ordinate of foreward. The analysis of data for estimation followed mainly papers of Ochi. These estimated data shall contribute for ship gull construction for basic optimum design. In particular, the estimated impact forces shall be given for the response of ship gull girder on the foreward flat bottom plate with characteristics of external forces.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2016.11a
• /
• pp.146-146
• /
• 2016

최근 국민 소득향상과 더불어, 여가시간 증가에 따라 해양레저에 대한 관심이 크게 높아지고 있으며, 그에 따라 레저용 선박 수요도 증가하고 있다. 기존 국내 소형 선박의 경우 FRP(fiber-reinforced plastic)재료로 선박을 건조해 왔다. 그러나 해양환경 규제 강화로 FRP 선박의 건조가 감소하고 있으며, 친환경 선박에 대한 필요성이 대두되고 있다. 따라서 FRP재료를 대체하는 선박용 재료로 친환경적이고 가벼운 소재인 알루미늄 합금 재료가 선박건조 분야에서 각광을 받고 있다. 특히 5000계열 Al-Mg 합금은 가공성과 용접성이 우수하여 주로 구조용으로 많이 사용되고 있으나 경량화에 따른 빠른 선속이 유체충격을 증가시켜 선체에 캐비테이션 손상을 일으킬 수 있다. Al-Mg 합금의 경우에 부식성이 대단히 큰 해양환경에서 부식과 캐비테이션 침식이 복합적으로 일어나면 손상이 빠르게 증가되는 경향을 나타내어 선박의 수명을 현저히 단축시켜 경제적인 손실을 초래한다. 따라서 본 연구에서는 해수 내에서 Al-Mg 합금의 캐비테이션 저항성을 향상시키기 위해 알루미늄 합금 표면에 내식성 뿐만 아니라 경도 및 내마모성 등의 기계적 특성이 우수한 산화피막을 형성시키는 양극산화 기술을 적용하고, 다양한 봉공처리(sealing)방법에 따른 캐비테이션 특성을 평가하였다. 캐비테이션 실험은 압전(piezoelectric) 효과를 이용한 진동발생 장치를 사용하여 $30{\mu}m$ 진폭으로 일정하게 유지하였으며, 시편과 혼 팁 사이의 간격은 1mm로 하였다. 캐비테이션 실험 후에는 시편을 초음파 세척하여 진공 건조기에서 24시간 이상 건조한 후 정밀저울로 무게를 측정하였으며, 표면 손상 형상을 분석하기 위해 주사전자현미경(SEM)과 3D현미경을 이용하여 관찰하였다.

• Journal of the Society of Naval Architects of Korea
• /
• v.46 no.2
• /
• pp.97-104
• /
• 2009

Ever increasing fuel prices, almost doubled in the last three years, and global pressure to reduce their environmental impact have been enforcing commercial vessel operators and designers to re-assess current vessel designs with emphasis on their propulsion systems and operational practices. In this paper the "Inclined Keel Hull (IKH)" concept, which facilitates to use larger propeller diameter in combination with lower shaft speed rates and hence better transport efficiency, is explored for a modern 3600 TEU container vessel with the aim of fitting an 13 % larger diameter propeller (and hence resulting 20% lower rpm) to gain further power saving over the similar size basis container ship with conventional "level keel" configuration. It appears that successful application of the "inclined keel Hull" concept is a fine balance amongst the maximum gain in propulsive efficiency, minimum increase in hull resistance and satisfaction of other naval architectural and operational requirements. In order to make the concept economically more viable, this paper concentrates on the fore body design with the possible combination of increase of volume in its fore body to recover the expected volume loss in the aft body due to the space for larger propeller and its low wave-making resistance to minimize the efficiency loss using a well-established optimization software.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.23 no.6
• /
• pp.731-738
• /
• 2017

Twin-hulls frequently incur structural damage at connecting members between the hull and deck induced by pitching motions during voyages. so, reasonable reinforcement is necessary around vulnerable spots such as corner knuckle, the chine bottom and inner hull. Since guidelines for structural design are not clear, engineers often respond by reinforcing plate thickness, changing stiffener sizes and reducing frame spacing, etc. These members constitute about 85 % of the longitudinal dimensions of the ship, so it is necessary to locally reinforce certain points to minimize weight stress, and also solve construction cost problems while securing the freeboard margin. Therefore, we developed a new program by analyzing the structural design procedures for the twin car-ferries based on Korean Register of Shipping (KR) High Speed Craft Rules, identifying items that need to be added. In order to ensure the reliability of buckling estimations for procedures and design programs, we conducted a comparative study with other standards and confirmed that differences were minimal.

• Journal of the Society of Naval Architects of Korea
• /
• v.38 no.3
• /
• pp.93-106
• /
• 2001

T-joint and hopper knuckle joint models are typical welded joints in ship structure, which are very susceptible to fatigue damage under service condition. Fatigue test and fracture mechanical analysis were performed on these joints to find out characteristics of fatigue behavior. Unified S-N curve was developed from the test results of these two types of joint using hot spot stress concept, and also propagation life was also estimated using Paris' crack propagation law. Residual stress effect on propagation life was considered in calculating propagation life, as was done with thermo-elasto-plastic FE analysis and residual stress intensity factor calculation. Fatigue life of similar kinds of welded joint could be predicted with this unified S-N curve and fracture mechanical analysis technique.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.30 no.1
• /
• pp.108-117
• /
• 2024

In this study, simulations based on computational fluid dynamics were performed for self-propulsion performance prediction of a catamaran that has asymmetrical inside and outside hull form and numerous knuckle lines. In the simulations, the Moving Reference Frame (MRF) or Sliding Mesh (SDM) techniques were used, and the rotation angle of the propeller per time step was different to identify the difference using the analysis technique and condition. The propeller rotation angle used in the MRF technique was 1˚ and those used in the SDM technique were 1˚, 5˚, or 10˚. The torque of the propeller was similar in both the techniques; however, the thrust and resistance of the hull were computed lower when the SDM technique was applied than when the MRF technique was applied, and higher as the rotation angle of the propeller per time step in the SDM technique was smaller in the simulations for several revolutions of the propeller to estimate the self-propulsion condition. The revolutions, thrust, and torque of the propeller in the self-propulsion condition obtained using linear interpolation and the delivered power, wake fraction, thrust deduction factor, and revolutions of the propeller obtained using the full-scale prediction method showed the same trend for both the techniques; however, most of the self-propulsion efficiency showed the opposite trend for these techniques. The accuracy of the propeller wake was low in the simulations when the MRF technique was applied, and slight difference existed in the expression of the wake according to the rotation angle of the propeller per time step when the SDM technique was applied.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.18 no.9
• /
• pp.480-485
• /
• 2017

The main reason for the heat induced accidents occurring at the after stern tube journal bearing is the excessive local pressure caused by the deflection of the propulsion shaft due to the propeller loads. It is expected that the contact area could beenlarged and the local pressure reduced accordingly by using a lining material having alow Young's modulus instead of the existing white metal. The purpose of this work is to investigate the characteristics of the pressure distribution and determine the allowable pressure value in the case where bearing products made of materials having a low Young's modulus are used. In this study, the propeller loads, heat effect, and hull deflection are considered in the evaluation of the local pressure of the ship propulsion shaft. Also, the Hertzian contact condition was applied. From the analysis results in the case where a lining material with a low Young's modulus was used, it was found that a robust design could be achieved and the local pressure could be reduced effectively independent of the load conditions. It will be possible to producenew products made of materials having a low Young's modulus if the manufacturer confirms the performance specifications drawn by this study.