• Journal of Navigation and Port Research
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• v.46 no.6
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• pp.491-500
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• 2022

It has been noted that an accurate estimation of wind loads on offshore structures such as an FLNG (Liquefied Natural Gas Floating P roduction Storage Offloading Units, LNG FPSOs) with a large topside plays an important role in the safety design of hull and mooring system. Therefore, the present study aims to develop a computational model for estimating the wind load acting on an FLNG. In particular, it is the sequel to the previous research by the author. The numerical computation model in the present study was modified based on the previous research. Numerical analysis for estimating wind loads was performed in two conditions for an interval of wind direction (α), 15° over the range of 0° to 360°. One condition is uniform wind speed and the other is the NPD model reflecting the wind speed profile. At first, the effect of sand-grain roughness on the speed profile of the NPD model was studied. Based on the developed NPD model, mesh convergence tests were carried out for 3 wind headings, i.e. head, quartering, and beam. Finally, wind loads on 6-degrees of freedom were numerically estimated and compared by two boundary conditions, uniform speed, and the NPD model. In the present study, a commercial RANS-based viscous solver, STAR-CCM+ (ver. 17.02) was adopted. In summary, wind loads in surge and yaw from the wind speed profile boundary condition were increased by 20.35% and 34.27% at most. Particularly, the interval mean of sway (45° < α <135°, 225° < α < 315°) and roll (60° < α < 135°, 225° < α < 270°) increased by 15.60% and 10.89% against the uniform wind speed (10m/s) boundary condition.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2022.06a
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• pp.108-109
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• 2022

In this study analyzed experimental data on noise interference caused by engine operating apply surface wave communication in the engine room. For the experiment, 7 areas of the engine room on 256 ton tug boat and measured noise during engine on off using signal analyzer for effect surface wave communication. In order to construct and actual communication network based on the analysis of the noise and confirm the characteristics of surface wave communication in the area made metal bulkheads the actual communication network installed communication equipment between three metal bulkheads and conducted a comparative experiment with wireless communication. The difference was confirmed. As a result, in the case of surface wave communication, there was no significant difference in the transmission and reception rates before and after engine operation in an environment with three bulkheads, but in the case of Wi-Fi using wireless, the performance deteriorated significantly during operation. was confirmed. As a result of analyzing the experimental data, it was confirmed that noise caused by engine operation affects wireless communication but does not affect surface wave communication. Therefore, even in the area with a lot of electromagnetic wave noise in the ship, when the surface wave communication system is configured using the ship's metal structure, it is possible to replace the wireless communication and furthermore, it is possible to apply the surface wave communication in the enclosed space and the engine room in the ship.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2021.11a
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• pp.127-128
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• 2021

This study suggests surface wave communication, which uses a metal surface as a medium, to provide wireless communication in the extreme environment due to surrounding metal materials on vessels. The test was conducted on a G/T 265 tons tug boat, and to confirm the possibility of surface wave communication between a bridge and each designated space in the boat. As a result, the transmission speed was 13Mbps in average. For the test case between the bridge and the engine room, transmission speed was 4.3Mbps while the engine was on, and 1.2Mbps during sailing. It was able to be overcome by partially changing the equipment installation location. Surface wave communication in a bow storage, a fully enclosed space, had 8Mbps better transmission speed than wireless communication; this confirmed the superiority of surface wave communication in confined spaces on a vessel. Additional surface wave generators were designed and applied to resolve the paint issue. It is expected to apply surface wave communication to implement the new wireless solution on vessels.

• Journal of Navigation and Port Research
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• v.47 no.6
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• pp.341-349
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• 2023

Gamcheon Port, which is one of three major harbors in the Port of Busan, is being operated to load, discharge and transport a wide range of cargoes, including general cargo, fisheries, steel products, cement, etc,. The harbor, designated as a compulsory pilotage area, provides pilotage services in compliance with relevant laws and regulations for arrival and departure of vessels in the Gamcheon Port area. Some academic research on the marine traffic environment in Gamcheon Port has been conducted. However, the pilotage environment and hazards to pilotage safety in the port have yet to be studied. Therefore, in this research, the pilotage environment and hazards to pilotage safety were identified, and it was confirmed that there are hazards to pilotage safety, such as vessels installed poor facilities including damaged pilot boarding arrangements, vessels blocking pilot's view by her structures and fishing nets, vessels unable to communicate in English, vessels not following VTS's order. The hazards to pilotage safety were also stratified, and the importance of the hazards was verified in accordance with a survey based on Analytic Hierachy P rocess(AHP) for Busan Harbor pilots, and safety measures to secure pilotage safety were examined to secure the safety of vessels calling Gamcheon Port.

• Journal of Navigation and Port Research
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• v.48 no.3
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• pp.164-170
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• 2024

The light buoy, a floating structure at sea, is prone to drifting due to external factors such as oceanic weather. This makes it imperative to monitor for any loss or displacement of buoys. In order to address this issue, the Ministry of Oceans and Fisheries aims to issue alerts for buoy displacement by analyzing historical buoy position data to detect patterns. However, periodic lifting inspections, which are conducted every two years, disrupt the buoy's location pattern. As a result, new patterns need to be analyzed after each inspection for location monitoring. In this study, buoy position data from various periods were analyzed using convex hull and distance-based clustering algorithms. In addition, the optimal data collection period was identified in order to accurately recognize buoy location patterns. The findings suggest that a nine-week data collection period established stable location patterns, explaining approximately 89.8% of the variance in location data. These results can improve the management of light buoys based on location patterns and aid in the effective monitoring and early detection of buoy displacement.

• Journal of the Korean earth science society
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• v.28 no.7
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• pp.914-924
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• 2007

This study is to compare differences in the depositional environments of natural beaches with those of beaches developed with artificial structures in the East Coast of Korea. Naksan-Osan beaches were selected for the examination of natural beaches and Anmok-Yumjun beaches for that of developed beaches. The study was performed on the foreshores and backshores of the selected beaches, and was based on the field research during the flood period of year 2004 and the dry period of year 2005. In Naksan-Osan beaches, pain size is fuel and sorting is better from northern coast to southern coast. Furthermore, sediment undergoes changes regularly and seasonal variations are small. But in Anmok-Yumjun beaches, grain size is coarser and sorting is worse than in Naksan-Osan beaches, showing irregular tendencies. The characteristic features of the two beaches would be effected by longshore currents which change along the type of coast line and have an effect on sediment. Especially, long shore currents interrupted by artificial structures in Anmok-Yumjun beaches may cause sedimental environment changes. In Anmok-Yumjun beaches, harbor expansions will be continued, and thus more changes are expected to occur in the beaches.

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.1
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• pp.82-89
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• 2016

In this study, we proposed a pier of pontoon-type, "Very Large Floating Structure" (VLFS), with the length of 500m, breadth of 200 m and height of 2 m in Yeosu domestic port. Since this structure ought to endure wave loads for long periods at sea, it is essential to analyze the wave response characteristics. Direct-method is used to analyze the fluid-structure problem and the coupled motion of equation is used to obtain response results. The structural part is calculated by using finite element method (FEM) and the fluid part is analyzed by using boundary element method (BEM). Dynamic responses caused by the elastic deformation and rigid motion of structure are analyzed by numerical calculation. To investigate response characteristics of the pier in regular waves, several factors such as the wavelength, water depth, wave direction and flexural rigidity of structure are considered. As a result, wave response of pier changed at the point of $L/{\lambda}$ 1.5 and represented the torsional phenomenon according to the various incident waves. And the responses showed increasing tendency as the water depths increase at the incident point in case of $L/{\lambda}=8.0$ and peak point of vertical displacement amplitude moved from side to side as the flexural rigidity of structure changes.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.29 no.6
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• pp.389-398
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• 2017

The re-analysis on the stable weight of the concrete armor unit (CAU) at the roundhead and the suggestion of the covering range at the roundhead with the increased weight of CAU were conducted. Tetrapods were applied to the tests and the three dimensional hydraulic tests were performed. The test results for the stable weight at the roundhead area were similar to the guides from Korean Design Standard for Harbour and Fishery Port (MOF, 2014) and Coastal Engineering Manual (USACE, 2005). The investigation of covering range at the roundhead of rubble mound structures armoured with Tetrapods was suggested that the length of five times of the design wave height from the tip of the superstructure was needed and appropriate. Both sides of the superstructure should be covered with increasing weighted CAU to satisfy the stability at roundhead area.

• Proceedings of KOSOMES biannual meeting
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• 2018.06a
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• pp.143-143
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• 2018

최근 3년간 환경관리해역(환경보전해역 및 특별관리해역)에서 이루어진 해역이용협의 검토 건수는 총 60건으로 조사되었다. 환경보전해역에서는 2015년 9건, 2016년 7건, 2017년 3건으로 지속적으로 감소하였고, 특별관리해역에서는 2015년 12건, 2016년 13건, 2017년 16건으로 증가하는 양상을 나타내었다. 환경관리해역의 개별사업 유형을 분석한 결과, 인공구조물 설치사업이 가장 높은 비율을 차지하였으며, 그 다음으로 항만 어항개발, 연안정비 및 해수 인 배수 사업유형이 많이 이루어진 것으로 분석되었다. 환경관리해역에서 국가해양환경정보통합시스템(MEIS) 자료를 참고하여 생태기반 해수수질 평가지수(WQI)와 경년별 수질변화경향을 비교한 결과, COD는 뚜렷한 증감의 변화는 보이지 않았으나 TN과 TP의 농도는 다소 감소하는 경향을 보였다. 특별관리해역인 광양만과 마산만 및 환경보전해역인 가막만에서는 빈산소수괴가 출현하였다. 이러한 환경관리해역에서의 이용 개발행위가 지속적으로 이루어지고, 이에 따른 해역이용협의서 등 해양환경부문 환경영향평가시에는 충분한 수질변화에 대한 실태분석 및 사업추진에 따른 수질영향을 철저히 진단해서 오염원관리에 대한 대책이 중점적으로 평가되어야 할 것으로 판단된다. 특히, 각 환경관리해역의 지정 목적에 따른 유지 수질목표를 명확히 설정할 필요가 있다. 또한, 개발사업에 따른 협의 평가과정에서의 검증을 위하여 환경관리해역에서의 수질 및 퇴적물에 대한 모니터링 및 분석결과에 대한 정도관리가 더욱 강화되어야 할 것이다.

• Journal of the Korean GEO-environmental Society
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• v.3 no.4
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• pp.19-27
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• 2002

Prediction of exact soil loss yield has as important engineering meaning as prediction of exact flow measurement in a stream. The quantity of soil loss in a stream should be considered in planning and management of water resources and water quality such as design and maintenace of hydraulic structures : dams, weirs and seawalls, channel improvement, channel stabilization, flood control, design and operation of reservoirs and design of harbors. In this study, the soil loss of Sap-gyo reservoir watershed is simulated and estimated by RUSLE model which is generally used in the estimation of soil loss. The parameters of RUSLE model are selected and estimated using slope map, landuse map and soil map by GIS. These parameters are applied to RUSLE's estimating program. And soil loss under probability rainfall in different frequencies are estimated by recent 30 years of rainfall data of Sap-gyo reservoir watershed.