• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2016.05a
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• pp.78-80
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• 2016

선박이 천수 영역에서 운항할 때, 선저부분의 압력변화로 인하여 흘수가 증가하는 현상이 나타난다. 이 같은 현상을 선체침하(Squat)라 하며, 선박의 조종성능을 변화시켜 해양사고의 발생위험을 높이게 된다. 특히, 초대형 선박의 경우에는 흘수가 커 천수영역에서의 선체침하현상이 더욱 크게 일어난다. 따라서 본 연구에서는 천수 영역에서의 초대형선박의 선체침하정도를 추정하고자 하였다. 이를 위하여, 세 가지 천수조건을 구성하고, 다양한 추정식을 이용하여 초대형선박의 경사각도에 따른 선체 침하의 정도를 계산하였으며, 그 결과를 비교하여 보여주었다.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2006.11a
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• pp.426-426
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• 2006

선박이 천 흘수 및 수로를 운항하는 경우 바닥과 벽면의 영향으로 인해 선체침하 및 비대칭적인 힘이 선체 주위에 발생하여 바닥이나 다른 선박 혹은 수로의 벽에 충돌하는 현상이 발생한다. 특히, 수로가 많은 유럽이나 북미를 운항하는 해운회사와 항해사들은 선박의 충돌을 방지하기 위해서 중요한 문제로 다루고 있다. 따라서, 본 연구에서는 선박의 안전한 항해를 위해 수치해석을 이용하여 선박과 벽면 사이에 발생하는 유체역학적 힘, 즉 Sway force와 Yaw Moment를 정성적으로 추정하고자 하였다. 천 흘수 유동 해석용 프로그램을 작성하였으며, 검증을 위해서 Wigley 선형에 적용하여 h/T별로 계산을 수행하여 시험결과와 비교하였다. 그리고, 벽면효과를 해석 할 수 있는 프로그램을 작성하여 실적선인 원유운반선 2척에 대하여 3가지 파라메터, 즉 선속, 수심 그리고 선박과 벽면 사이 거리의 변화에 따른 다양한 계산을 수행하였다. 계산된 결과는 시험결과 및 기 발표된 수치해석 결과와 비교하였다. 기 발표된 논문에서는 시험결과와 계산결과가 상이한 결론을 보여 주었는데, 그 이유는 수치해석에 있어서 자유표면 문제를 선형화된 자유표면 조건식을 사용한 부분을 가장 큰 이유로 언급하였다. 하지만, 본 연구의 결과는 Sway force와 Yaw Moment가 기 발표된 논문의 시험결과와 정성적으로 일치함을 보여 주었다. 본 연구를 통해 수치해석 방법으로 선박에 작용하는 비대칭 유동에 대한 유체역학적인 힘을 정성적으로 추정할 수 있었고, 제한된 수로에서 선박의 조종성 예측 및 수로 설계시 유용한 정보를 제공할 수 있을 것이라고 판단되어 진다.

• Journal of Navigation and Port Research
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• v.38 no.1
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• pp.19-27
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• 2014

When a ship operates in a shallow water and channel, the hull sinkage and asymmetrical force generated around the ship by the influence of sea bottom and bank walls are caused collision with sea bottom, other ships or the bank itself. Especially, the shipping company and pilots navigating the area of Europe and North America with many channels are deal with it as a important matter to prevent collision. In this paper, hydrodynamic force generated between the ship and bank using the numerical analysis for the safe navigation of ship, that is, sway force and yaw moment should be presumed qualitatively. It makes a program for fluid analysis of the shallow water and bank effect. Analyses are carried out for three kind of parameter, that is, ship's speed, water depth and ship-bank distance for crude oil carriers. The numerical analysis results are compared with results of the experiments and the previous published papers.

• Journal of Ocean Engineering and Technology
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• v.15 no.1
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• pp.1-6
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• 2001

This study focuses on the potential flow analysis for a hull with the transom stern. The method is based on a low order panel method. The Kelvin type free-surface boundary condition which is known to better fit experimental data for a high speed is applied. To treat a dry transom stern effect a special treatment for the free-surface boundary condition is adopted at the free-surface region after the transom stern. Trim and sinkage, which are important in high speed ships, are considered by an iterative method. Pressure and momentum approaches are used to calculate the wave resistance. Numerical calculations are performed for Athena hull and these results are compared with the experimental data and also other computational results.

• Journal of Navigation and Port Research
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• v.37 no.1
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• pp.1-7
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• 2013

In this paper the developed prediction technique of wave-making resistance performance for a ship attached with a vertical blade had been verified. Numerical analysis program as a prediction technique had been developed using the Rankine source panel method and the vortex lattice method(VLM). The nonlinearity of the free surface conditions was fully taken into account using the iterative method and the trim and the sinkage of the ship were also considered in the numerical analysis program. Panel cutting method was applied to get hull surface panels. Numerical computations were carried out for a 4000TEU container carrier and the vertical blade was attached 6 different locations astern. To investigate the validity of the numerical analysis program the commercial viscous flow field analysis program FLUENT was used to obtain the viscous flow field around the ship and the model test was performed. The model test results were compared with the numerical analysis results.

• Journal of the Society of Naval Architects of Korea
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• v.38 no.1
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• pp.9-26
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• 2001

In this paper. the development of a pusher-barge hull form which enables the continuous transportation along the coast and canal is performed. For the design stage of the hull forms. these are developed for Kyungin canal which is will be drawn up as the next contribution project of the Korean government are adopted. The model tests for the designed ship are carried out in the Inha University Towing Tank and the numerical simulations are done with a finite difference method based on MAC scheme. At first, the experiments are performed with designed model ships from low speed to high speed including service speed(6knots) among the corresponding designed speed. Resistance characteristics of designed ships are compared with experimental results of other several pusher-barge hull shapes. Next, the numerical simulations are performed for three cases, that is pusher only, barge only and pusher-barge condition in the designed speed. Each calculations are carried out in deep and restricted water condition. The flow characteristics around hulls in the latter condition are compared with those in the former condition.

• Journal of Navigation and Port Research
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• v.27 no.5
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• pp.465-471
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• 2003

A coastwise chemical tanker sailing at full speed has capsized during turning in calm water. In the previous paper, we investigated the reasons of the accident by demonstrating the proper correction for the free surface effect of the liquid cargo and the bow-sinkage effect. In this paper, we also carry out model experiments of a transverse pressure under the seawater and an outward heel moment according to the heel angle and rudder angle, on the basis of radius of turning circle, ship's speed and drift angle of model ship occurring in turning. It is also shown that the flooding of seawater onto the deck occurring in turning generated a significant outward heel moment and increased the vertical distance between the center of gravity of the ship and the center of lateral water drag.

• Journal of the Korean Society of Marine Environment & Safety
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• v.20 no.2
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• pp.172-178
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• 2014

This study suggests the minimum critical external forces based on the assessment of anchoring safety to single anchor situation for representative 8 number of ships in E-group anchorage of Ulsan port. Assessment of anchoring safety is compared holding powers of anchor with external forces of wind, wave and current. Holding powers was reflected materials of seabed, equipment numbers regarding anchor and chain weight, also external forces acting on a hull was calculated considering projected wind area and wetted surface area to the full and ballast conditions respectively. The results of anchoring safety assessments to single anchor showed that the minimum criteria of dragging anchor is a little different from ship's type, size and loading conditions. Bulk carrier can be dragged over the 15m/s of winds and Tanker can be dragged over the 13m/s of winds in case of less than 2knots of currents speed.

• Journal of the Society of Naval Architects of Korea
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• v.34 no.4
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• pp.72-83
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• 1997

The purpose of present study is to find an appropriate hull shape of a container ship which can operate along the coast and through canals. A 200TEU class container ship is designed with dimensional modifications of an existing 140TEU container ship which is a domestic coastwise vessel. For the fore-body shape including bulbous bow. additional modification is done by changing the sectional area curve and frameline shape using the data of series resistance test. The model tests are performed in the towing tank to measure total resistance sinkage and trim of the model. And a finite-difference method based on MAC method is utilized to analyze the flow field around the ships in deep and restricted water. From the result of model test and numerical analysis, the resistance characteristics of the designed hull form are predicted.

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.7
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• pp.863-868
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• 2016

In this study, the precise shapes of sunken ships and information on seafloor topography were analyzed using data obtained from a multi-beam echo sounder. The state of each sunken ship was analyzed by processing diverse imagery data which was compared with data obtained from past investigations to determine changes in the state and circumjacent seafloor topography. Apparent changes in the seafloor topography around one sunken ship, the "Pacific Friend", were found from stern to bow as a result of continued submarine erosion and sedimentation. In the case of sunken ship "No. 7 Haeseong", the partial collapse of the bow was revealed in the seabed images captured in 2015, though it had still been intact in images captured during the Korea Hydrographic and Oceanographic Agency's investigation in 2011. This partial collapse was presumed to have resulted from the effects of continued tidal currents, the cargo load of the ship and continued corrosion of the ship over a long time on the seabed. Continuous monitoring of residual fuel inside the ship is necessary to avoid leakage and potential marine pollution. By conducting image analysis on these sunken ships, it has been determined that the structural safety of the ships is seriously influenced by tidal currents and seafloor topography, while the hulls will be continuously changed by corrosion. As a result, it can be concluded that the development of prediction and response techniques that take into consideration residual fuel leakage and environmental changes according to the geological characteristics of sunken ships is necessary.