The Evaluation of Ship Motions in a Harbor along the Entrance Channel by Field Observation

Ik-Soon Cho 한국항해항만학회 2005 한국항해항만학회지 Vol.29 No.9

Maritime transportation consists of various situations such as navigation in the ocean, ship handling at harbor entrances, cargo handling and mooring in harbors. Generally, ships are built for the purpose of carrying people and materials upon the seas. In order to accomplish the mission, a ship must be built to withstand the rigors of heavy weather and waves. In particular, the safety of ship motions at the entering/departing harbor and mooring under the effects of waves is very important for ship operation from the viewpoint of marine engineering. Therefore, safety and efficiency during entrance, departure, and mooring are extremely important aspects in the evaluation of ship operations from viewpoints of ship motions. However, the ship motions near a harbor entrance are not observed or studied as much. In this paper, to evaluate the difficulty of ship operations, field observations were performed using a new observation system with high accuracy in typhoon seasons, and grasp was done concerning about the time series characteristic that ship motions change rapidly within a harbor. Namely, such observations enable the quantitative safety evaluation under the effects of waves during ships entering and departing harbors in heavy weather.

A Safety Evaluation of Moored Ship Motions by Observed Tsunami Profile

Ik-Soon Cho,Masayoshi Kubo,Gil-Young Kong,Yun-Sok Lee,Choong-Ro Lee 한국항해항만학회 2006 한국항해항만학회 학술대회논문집 Vol.1 No.-

Recent warnings indicate that there is a potential risk of massive earthquake in Japan within 30 years. These earthquakes could produce large-scale tsunamis. Tsunamis are very powerful and can be traveled thousands of miles and caused damage in many countries. Consideration of the effect of tsunami to the moored ship is very important because it brings the loss of life and vast property damage. In this paper, the numerical simulation procedure to analyze the motions of a moored ship due to the observed waves of tsunami, Tokachi-off earthquake tsunami profile in northern Pacific coasts of Japan on September 26 in 2003. And the effects on the motions and mooring loads are investigated by numerical simulation. Numerical simulations consist of hydrodynamic analyses in a frequency domain and ship motion analyses in a time domain as the motions of moored ships are examined. As the process begins, the hydrodynamic and wave- exciting forces for moored ships must be calculated. Ship motions and mooring forces can then be calculated by solving the equations of motion. In order to investigate the safety evaluation on the motions of moored ship by tsunami attack, we applied a numerical simulation procedure to a 135,000m3 LNG carrier moored at an offshore sea berth.

The Evaluation of Ship Motions in a Harbor along the Entrance Channel by Field Observation

Cho Ik-Soon Korean Institute of Navigation and Port Research 2005 한국항해항만학회지 Vol.29 No.9

Maritime transportation consists of various situations such as navigation in the ocean, ship handling at harbor entrances, cargo handling and mooring in harbors. Generally, ships are built for the purpose of currying people and materials upon the seas. In order to accomplish the mission, a ship must be built to withstand the rigors of heavy weather and waves. In particular, the safety of ship motions at the entering/departing harbor and mooring under the effects of waves is very important for ship operation from the viewpoint of marine engineering. Therefore, safety and efficiency during entrance, departure, and mooring are extremely important aspects in the evaluation of ship operations from viewpoints of ship motions. However, the ship motions near a harbor entrance are not observed or studied as much. In this paper, to evaluate the difficulty of ship operations, field observations were performed using a new observation system with high accuracy in typhoon seasons, and grasp was done concerning about the time series characteristic that ship motions change rapidly within a harbor. Namely, such observations enable the quantitative safety evaluation under the effects of waves during ships entering and departing harbors in heavy weather.

대형 LNG 선박의 롤 선체운동 추정에 관한 연구

송재영,이춘기,임정빈 한국항해항만학회 2020 한국항해항만학회지 Vol.44 No.3

The ship motion of large LNG ships affects ships’ safety. The purpose of this study was to estimate the transfer function of roll motion among the hull motion of 153,000 m3 class LNG vessels. The ship motion transfer function was modeled using a Linear Time-Invarient system with single input, single output, and transfer function. The transfer function of the ship motion was estimated by the system identification method using single ocean wave as input of the model, and using the roll motion of the LNG ship obtained through ANSYS as the output of the model. The usefulness of the experimental results was evaluated using the precision and estimation rate of the model for cases wherein the different transfer function dimensions. Results of the experiment showed a precision at 99% and 98%, with estimation rate at 78% and 50%. From these results, we found the proposed method of estimating the transfer function of ship motion in this study reasonable. In the future, data of ship motion in actual sea conditions will be acquired and it will be applied to make the construction of models with multiple inputs and multiple outputs for practical use. 대형 LNG 선박의 선체 운동은 선박의 안전에 영향을 미친다. 본 연구의 목적은 153,000 m3 급 대형 LNG 선박의 선체 운동 중에서 롤 운동에 대한 전달함수를 추정하기 위한 것이다. 단일-입력과 단일-출력 그리고 시스템 전달함수를 갖는 선형 시 불변(Linear Time-Invarient) 시스템을 이용하여 선체 운동 전달함수를 모델링 하였다. 모델의 입력으로 단일 해양파를 이용하고, 모델의 출력으로는 ANSYS를 통해서 획득한 LNG 선박의 롤 운동을 이용하여 시스템 식별법을 기반으로 선체 운동의 전달함수를 추정하였다. 실험 결과의 유용성은 전달함수 차원이 서로 다른 경우에 대한 모델의 안정도와 추정률을 이용하여 평가하였다. 실험 결과 안정도는 99%와 98%로 나타나고, 추정률은 78%와 50%로 나타났다. 이러한 결과로부터, 본 연구에서 제안한 선체 운동 전달함수 추정 방법이 타당함을 알았다. 향후, 실제 해상에서 운항 중인 선박의 선체 운동 데이터를 획득하여 다중-입력 그리고 다중-출력을 갖는 모델 구축에 적용하여 실용화를 추진할 예정이다.

Effect of wave periods on added resistance and motions of a ship in head sea simulations

Seo, Seonguk,Park, Sunho,Koo, BonYong Elsevier 2017 Ocean engineering Vol.137 No.-

<P><B>Abstract</B></P> <P>Given that the International Maritime Organization (IMO) recently introduced the Energy Efficiency Design Index (EEDI) for new ships and the Energy Efficiency Operational Indicator (EEOI) for ship operations, accurate prediction of the added resistance of ships advancing in waves has become necessary. In the present study, the open-source computational fluid dynamics library, OpenFOAM, was used to predict the added resistance with the motions of a ship. Unstructured grid using a hanging-node and cut-cell method was used to generate fine grid around a free-surface and ship. Five wavelengths from a short wavelength (<I>λ/L</I> <SUB> <I>PP</I> </SUB>=0.65) to a long wavelength (<I>λ/L</I> <SUB> <I>PP</I> </SUB>=1.95) were considered as head waves. The grid uncertainty was evaluated with respect to three grid systems for a wavelength of <I>λ/L</I> <SUB> <I>PP</I> </SUB>=1.15. The predicted added resistance and heave and pitch motions with various head waves were compared with the data from model experiments. The wave pattern around the ship and the motions of the ship were analyzed with respect to the wave encounter period. When the wavelength was similar to the ship length, the ship moved against the waves, and thus the added resistance was greater compared with other wavelengths.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Added resistance is small in waves with short and long wavelengths. </LI> <LI> When wavelength is similar to ship length, ship moves against waves. </LI> <LI> Long wavelength makes to easier prediction of added resistance. </LI> <LI> Vortices structures around stern by ship motions are presented. </LI> </UL> </P>

항만공진주기와 선박동요량을 고려한 항만가동율 산정

곽문수(Moonsu Kwak),문용호(Yongho Moon) 한국해안해양공학회 2015 한국해안해양공학회 논문집 Vol.27 No.1

본 연구는 선박의 크기, 계류조건, 파랑의 주기, 파향 등에 의한 계류선박의 동요량을 해석하고 선박의 하역한계파고 산정 및 항만가동율을 평가하는 방법을 제시한 것이다. 본 방법은 포항신항 제8부두의 파랑관측자료를 이용하여 타당성을 검증하였다. 하역중단 시 파랑관측 자료는 파고 0.10~0.75 m, 주기 7~13 s 이었으며, 이때 계류된 선박은 800~35,000톤 이었다. 그리고 본 방법으로부터 산정된 제 8부두의 하역한계파고는 선박 5,000, 10,000, 30,000톤에 대하여 파고 0.19~0.50 m, 주기 8~12 s로 산정되었다. 본 방법의 결과는 연구대상 선박의 크기가 현지 선박의 크기와 정확히 일치하지는 않아서 파고는 관측치와 다소 차이를 보이지만 주기변화에 따라 하역한계파고를 잘 재현하고 있음을 알 수 있었다. 그리고 파향이 75도 인 경우의 본 방법에 의한 하역한계파고는 현행 항만설계 기준에 제시된 한계파고 보다 장단주기 파를 고려하면 16~62% 감소하였고, 단주기 파랑만 고려하면 0~46%감소하였다. 특히 현행 항만설계기준의 하역한계하고는 10,000톤 이하의 선박에 대해서는 과대 평가되었음을 확인할 수 있었다. 한편, 선박의 동요량을 고려하여 산정된 포항신항 제 8부두의 가동율은 설계기준 파고에 의한 가동율 에 비하여 6.5% 감소하였다. This study proposed an estimation method of allowable wave height for loading and unloading of the ship and evaluation of effective working days considering moored ship motion that is affected by sip sizes, mooring conditions, wave periods and directions. The method was examined validity by comparison with wave field data at pier 8<SUP>th</SUP> in Pohang New Harbor. The wave field data obtained with wave height of 0.10~0.75 m and wave period of 7~13 s in ship sizes of 800~35,000 ton when a downtimes have occurred. On the other hand, the results of allowable wave height for loading and unloading of the ship in this method have obtained with wave heights of 0.19~0.50 m and wave periods of 8~12 s for ship sizes of 5,000, 10,000 and 30,000 ton. Thus this method well reproduced the field data respond to various a ship sizes and wave periods. And the results of this in Korea are didn’t respond to various the ship sizes and wave periods, and we h method tended to decrease in 16~62 percent when have considered long wave, and it is decreased in 0~46 percent when didn’t consider long wave than design standards in case of the ship sizes of 5,000~30,000 ton, wave period of 12 s and wave angle of 75°. The allowable wave heights for loading and unloading of the ship proposed by design standards in Korea have found that overestimated on smaller than 10,000 ton. On the other hand, the rate of effective working days considering ship motion at pier 8<SUP>th</SUP> in Pohang New Harbor reduced in 6.5 percent when compare with the results without considering ship motion.

무인항공기 함상착륙을 위한 함정운동 추정 및 예측

김기준,이광현,허기봉,김유단,김승균,석진영 한국항공우주학회 2014 한국항공우주학회 학술발표회 논문집 Vol.2014 No.4

본 논문에서는 해상환경에 따른 함정운동을 추정 및 예측 하였다. 해상에서의 함정운동은 파도의 조건과 바람등 외부조건에 따라서 항시 변화한다. 이러한 함정에 무인항공기가 이착륙 하려면 함정의 운동을 정확히 추정하고 예측하는 과정이 필요하다. 본 논문에서는 함정운동을 모사하기 위해서 MSS Hydro Toolbox를 사용하여 함정의 운동을 시뮬레이션 하였다. 함정의 히브(heave), 피치(pitch), 롤(roll) 움직임을 무향 칼만필터를 이용하여 추정하고 추정된 결과를 바탕으로 15초 동안 함정의 움직임을 예측하였다. 또한 300회의 몬테카를로 시뮬레이션을 통하여 필터의 강건성을 확인하였다. This paper presents estimation and prediction of ship motion depending on sea state. Ship motion at sea, constantly changes depending on the external conditions such as wave and wind conditions. Accurate estimation and prediction of the ship motion is essential for automatic take-off and landing of UAVs. The MSS Hydro Toolbox is used for ship motion simulation. The ship"s heave, pitch, roll motions are estimated using unscented kalman filter. Also ship motion prediction for 15 seconds is performed without the measurement. In addition, monte-carlo simulations verify the robustness of the UKF.

선박 자율 운항을 위한 선박운동제어에 관한 연구

김경현 ( Kyong-hyon Kim ),김영복 ( Young-bok Kim ),지상원 ( Sang-won Ji ) 한국수산해양기술학회(구 한국어업기술학회) 2018 수산해양기술연구 Vol.54 No.3

In this study, a ship motion control system design method is introduced for autonomous ships. Some related research results and technologies for autonomous ships have already been developed and applied to ships. For example, the Norwegian Maritime Authority and the Coastal Administration have signed an agreement that allows to test of autonomous ships in the defined area (port to port). Many countries and industries are pursuing to realize the autonomous vessel in the real world. In this paper, the authors try to develop related technology. As basic research, a ship model of the pilot vessel is developed and physical parameters are identified by experiment and simulations. Using the mathematical ship model, a control system is designed and control performance is evaluated by simulations.

A Study on Construction of Collision Reproducing Simulator and Application to Analysis of Marine Casualty

Sohn, Kyoung-ho,Bae, Jun-young Korean Institute of Navigation and Port Research 2004 한국항해항만학회지 Vol.28 No.2

Ships' collision accident has often occurred in congested waterways or in harbour areas. To examine the cause of collision accident may be necessary to prevention against another similar one. We discuss the construction of ship-manoeuvring-simulator system used for reproducing ships' collision phenomenon The system consists of one simulator bridge for own ship and two control consoles for own ship and target ship. Own ship and target ship are linked each other, and are simultaneously manoeuvred in simulator bridge or at control console respectively. And a simulator experiment for reproducing ships' collision phenomenon and for examining the cause of accident is carried out. Through the present case study, we find out that the constructed simulator system is very useful for reproducing ships' collision phenomenon and for examining the cause of accident.

함정운동에 의해 발사대 해치에 작용하는 외란에 관한 연구

변영철(Young-Chul Byun),강이석(E-Sok Kang) 제어로봇시스템학회 2013 제어·로봇·시스템학회 논문지 Vol.19 No.12

In this paper, the disturbance applied to launcher hatch by ship motions is introduced to identify the vertical ship motion disturbance. Basically, ship motions are comprised of 6 degrees of freedom: roll, pitch, yaw, heave, surge and sway. In the case of the shipboard launcher hatch the coupled pitch, heave and roll are significant motions to be transformed to a vertical direction motion. The maximum acceleration values are obtained from the vertical motion model and the ship motion data in accordance with ship type and hatch location on the ship. We verify that the maximum pitch motion mainly influences the launcher hatch and also present the quantity of the maximum load disturbance by the ship’s motion acceleration.