• International Journal of Naval Architecture and Ocean Engineering
• /
• 제3권1호
• /
• pp.86-94
• /
• 2011

This paper compares frequency domain and time domain predictions from the ShipMo3D ship motion library with observed motions from model tests and sea trials. ShipMo3D evaluates hull radiation and diffraction forces using the frequency domain Green function for zero forward speed, which is a suitable approach for ships travelling at moderate speed (e.g., Froude numbers up to 0.4). Numerical predictions give generally good agreement with experiments. Frequency domain and linear time domain predictions are almost identical. Evaluation of nonlinear buoyancy and incident wave forces using the instantaneous wetted hull surface gives no improvement in numerical predictions. Consistent prediction of roll motions remains a challenge for seakeeping codes due to the associated viscous effects.

• 대한조선학회지
• /
• 제25권3호
• /
• pp.3-12
• /
• 1988

A natural or an artificial harbor can exhibit frequency(or period) dependent water surface oscillations when excited by incident waves. Such oscillations in harbors can cause significant damage to moored ships and adjacent structures. This can also induce undesirable current in harbors. Many previous investigators have studied various aspects of harbor resonance problem. In the percent paper, both a localizes finite element method(LFEM) which is based on the functional constructed by Chen & Mei(1974) and Bai & Yeung(1974) and an integral equation method which was used by Lee(1969) are applied to harbor resonance problem. The present method(LFEM) shows computationally more efficient than the integral equation method. Our test results shows good agreement compared with other results. This enhanced computational efficiency is due to the fact that the present method gives a banded symmetric coefficients matrix and requires much less computational time in the calculation of the influence coefficients matrix than the integral equation method involved with Green's function. To test the present numerical scheme, two models are treated here. The present method(LFEM) can be extended to a fully three dimensional harbor problem with the similar computational advantage.

• International Journal of Naval Architecture and Ocean Engineering
• /
• 제6권1호
• /
• pp.132-150
• /
• 2014

In this study, the inertial properties of fully filled liquid in a tank were studied based on the potential theory. The analytic solution was obtained for the rectangular tank, and the numerical solutions using Green's 2nd identity were obtained for other shapes. The inertia of liquid behaves like solid in recti-linear acceleration. But under rotational acceleration, the moment of inertia of liquid becomes small compared to that of solid. The shapes of tank investigated in this study were ellipse, rectangle, hexagon, and octagon with various aspect ratios. The numerical solutions were compared with analytic solution, and an ad hoc semi-analytical approximate formula is proposed herein and this formula gives very good predictions for the moment of inertia of the liquid in a tank of several different geometrical shapes. The results of this study will be useful in analyzing of the motion of LNG/LPG tanker, liquid cargo ship, and damaged ship.

• 대한조선학회논문집
• /
• 제50권3호
• /
• pp.145-152
• /
• 2013

Recently, with oil price jumping and environmental issues, Green ship is paid deep attention to by ship owner, operator, builder, class and government. Fuel efficiency and reduction of $CO_2$ emissions are expected to have a strong influence on the design and operation of merchant ships. Many ship owners and operators are seeking the more economic method by the best operating route and the application of reliable and effective energy saving devices. With the Energy Efficiency Design Index (EEDI) in 2013 attention will more than ever be focused at achieving maximum fuel economy in the hydrodynamic design of hull forms, their appendages and propellers. IMO requirements for $CO_2$ emission for ships will now be implemented for vessels ordered from 1st January 2013. So far, a lot of new idea and patents have been proposed, tested, claimed and applied for various kinds of ship type. This paper shows numerical and experimental work related to a study on a energy saving devices particularly for fuller ship such as merchant vessel of Tanker and Bulker. From the bare hull wake measurements, typical upper/lower asymmetry of hull wake at the propeller disk was found. The pre-swirl duct have been designed and reviewed to recover the loss of propeller running in that condition. The general function of the pre-swirl duct was set to work against this asymmetry of wake and generate pre-swirled flow into the propeller against the propeller rotating direction.

• 수산해양기술연구
• /
• 제23권3호
• /
• pp.1-1
• /
• 1987

이상으로부터 다음의 결론을 얻는다. 조파저항 이론의 전개에서 Michell 적분보다 더욱 정밀한 Neumann-Kelvin 문제가 복잡한 kernel 함수 때문에 많은 시간과 노력이 필요하지만, 원점 부근에서 Kelvin 소오스의 점근거동을 조사하여 세장체 근사를 행함으로 N-K 문제의 kernel 함수에 대한 근사와 동등하게 처리될 수 있었다. 조파저항의 계산 결과가 Michell 적분과 비슷한 경향을 보이나, 실험치와의 정확한 비교를 할 수 없었다. 그러나 세장선 이론을 적용함으로써 훨씬 복잡하고 지루한 작업을 들 수 있었다. 전진 속도를 갖는 경우에는 수정된 Green정리를 이용하면 될 것으로 기대된다.

• 한국해양환경ㆍ에너지학회지
• /
• 제8권1호
• /
• pp.39-45
• /
• 2005

2004년 11월 러시아의 교토의정서 비준에 의하여 2005년 2월에 교토의정서의 발효를 앞두고 있다. 따라서 1차 감축대상국은 2008년부터 2012년까지 1990년 대비 각 국가당 설정된 GHG(Green House Gas)배출량을 감축해야하는 상황에 처해 있다. 본 논문에서는 대기 중에 뿜어내는 GHG중 가장 많은 비율을 차지하는 CO₂를 심해에 친환경적으로 처리하는 기술로서 해양격리기술에 대해 소개한다. 본 해양격리기술은 4개의 주요단계로 구분할 수 있는데, 해양수송기술, 해양분사기술, 해양저장효율평가기술, 해양처리생태영향 평가기술등으로 나눌 수 있다. 본 논문에서는 CO₂의 해양 분출시에 초기희석율에 영향을 미치는 해양분사기술 중, 액포의 거동과 용해에 관한 기초 연구를 수행하였다. 특히 본 연구에서는 전산유체역학 기법 (Computational Fluid Dynamics)을 통해 해수를 연속상(Continuous phase), 액적을 분산상(Disperse phase)으로 한 이상(Two-phase) 유체를 3차원 이동형 비구조 격자와 유한체적법을 이용하여 상 경계면이 거동하면서 거동에 따른 용해도의 변화를 추정하였다 따라서, 본 연구는 액적의 거동과 용해도의 유체역학적 관계를 밝히는 데 기초적 자료가 될 것으로 판단된다.

• 대한조선학회논문집
• /
• 제54권3호
• /
• pp.196-203
• /
• 2017

In general, the installation of offshore wind turbine have been carried out by a jack-up barge or wind turbine installation vessel. In case of using jack-up barge, an additional barge is required to transport offshore wind turbines. During the transportation, barge is affected by environmental conditions such as wave, wind etc. So, it is important to secure the static and dynamic stability of the barge. In this study, fundamental research was performed to evaluate the stability of barge due to use the guide frame. The analysis for static stability of barge was performed under the two loading conditions with or without wave and those results were evaluated according to the Ministry of Oceans and Fisheries rules. Also motion analysis was performed under the ITTC wave spectrum using buoy data and evaluated based on NORDFORSK guideline by using commercial software Maxsurf Motions.

• Journal of Advanced Marine Engineering and Technology
• /
• 제37권8호
• /
• pp.849-854
• /
• 2013

선박 운항의 경제성, 효율성 및 편리성을 높이면서 친환경 선박에 대한 연구가 지속적으로 이루어지고 있다. 이 중 하나가 전자제어식 디젤 엔진의 개발이다. 자동차용 소형에서는 이미 전자제어식 디젤기관이 주류를 이루고 있으나 선박에서는 안정성 및 신뢰성의 문제로 보급에 어려움을 겪고 있다. 본 연구에서는 이러한 문제를 해결하기 위하여 전자제어식과 캠식 엔진이 동시에 탑재되어 있는 한국해양대학교의 실습선 한바다호의 주기관을 이용하여 두 엔진의 성능을 비교 분석하였다. 그 결과 전자제어식 디젤엔진의 연료소비율이 저감되었으며 특히 저부하에서의 성능이 보다 우수하였다. 또한 연료소비율에 있어서 해상 시운전에서 훨씬 효과적이었다.

• 한국해양공학회지
• /
• 제29권6호
• /
• pp.418-426
• /
• 2015

Recently, shipping operators have been making efforts to reduce the fuel cost in various ways, such as trim optimization and bulb re-design. Furthermore, IMO restricts the hydro-dioxide emissions to the environment based on the EEDI (Energy Efficiency Design Index), EEOI (Energy Efficiency Operational Indicator), and SEEMP (Ship Energy Efficiency Management Plan). In particular, ship speed is one of the most important factors for calculating the EEDI, which is based on methods suggested by ITTC (International Towing Tank Conference) or ISO (International Standardization Organization). Many shipbuilding companies in Korea have carried out speed trials around the Korea Straits. However, the conditions for these speed trials have not been exactly the same as those for model tests. Therefore, a ship’s speed is corrected by measured environmental data such as the seawater temperature, density, wind, waves, swell, drift, and rudder angle to match the conditions of the model tests. In this study, fundamental research was performed to evaluate the ship resistance performance due to changes in the water temperature and salinity, comparing the ISO method and numerical simulation. A numerical simulation of a KCS (KRISO Container ship) with a free-surface was performed using the commercial software Star-CCM+ under three conditions that were assumed based on the water temperature and salinity data in the Korea Straits. In the simulation results, the resistance increased under low water temperature & high salinity conditions, and it decreased under high water temperature & low salinity conditions. In addition, the ISO method showed the same result as the simulation.

• Journal of Advanced Marine Engineering and Technology
• /
• 제40권9호
• /
• pp.791-798
• /
• 2016

본 연구에서는 상용 점성 유동 해석 소프트웨어인 Star-CCM+를 이용하여 110m급 해양작업지원선의 빌지킬 효과에 따른 횡동요 성능에 관한 연구를 수행하였다. 해양작업지원선에 관한 연구에 앞서 DTMB 5512 선형에 대한 수치 시뮬레이션을 통해 실험과 비교 검증하였다. 검증된 결과를 바탕으로 빌지킬 유무에 따른 해양작업지원선의 자유 횡동요 시뮬레이션을 수행하였으며, 이를 통해 각각의 무차원 감쇠 계수와 횡동요 응답진폭함수를 산출하였다.