• 제목/요약/키워드: extreme ocean conditions

검색결과 89건 처리시간 0.022초

터렛 계류된 LNG-FSRU의 극한 계류 해석 (Extreme Mooring Analysis of Turret Moored LNG-FSRU)

  • 이민경;정광효;박성부;유병석;정윤석
    • 대한조선학회논문집
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    • 제53권5호
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    • pp.435-446
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    • 2016
  • In this study, hydrodynamic and mooring analysis for LNG FSRU moored by an internal turret with 9 mooring lines are numerically performed using commercial softwares, Hydrostar and Ariane. Met-ocean combinations for screening method are taken from wave governed condition(BV Rule Note NR 493) with relative heading between wave and wind between −45° and +45° and relative heading between wind and current between −30° and +30°. Extreme mooring analysis and sensitivity analysis are performed for intact and damaged (=one line missing) conditions and the parameters for sensitivity analysis are wave peak period, peak enhancement factor and line pretension. In the viewpoint of the design tension in mooring line, chain diameter is designed to satisfy safety factor for each conditions. As the chain diameter is increased from 152mm to 171mm, the designtension is reduced while the minimum breaking load is increased.

부산 송도해수욕장의 해안선변화 특성 분석 (Characteristic Analysys of Songdo Beach, Busan, Shoreline Changes)

  • 김명규;윤종성
    • 한국해양공학회지
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    • 제24권1호
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    • pp.53-59
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    • 2010
  • In this study, an investigation of the shoreline changes at Song-do beach in Busan was carried out for a coastal improvement project to prevent damage from coastal disasters. From the results of the observed data, it is seen that the shoreline moves seaward under extreme wave conditions and moves leeward under normal wave conditions. The reason for this is wave run-up when wave conditions are extreme in summer. In addition, nourishment sand is moved seaward by wave run-up. Thus, the shoreline's slope is gently decreased. Therefore, the shoreline is moved seaward.

Anti-icing Method of Heated Walkway in Ice Class Ships: Efficiency Verification of CNT-based Surface Heating Element Method Through Numerical Analysis

  • Woo-Jin Park;Dong-Su Park;Mun-Beom Shin;Young-Kyo Seo
    • 한국해양공학회지
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    • 제37권5호
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    • pp.215-224
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    • 2023
  • While melting glaciers due to global warming have facilitated the development of polar routes, Arctic vessels require reliable anti-icing methods to prevent hull icing. Currently, the existing anti-icing method, i.e., the heating coil method, has disadvantages, such as disconnection and power inefficiency. Therefore, a carbon nanotube-based surface heating element method was developed to address these limitations. In this study, the numerical analysis of the surface heating element method was performed using ANSYS. The numerical analysis included conjugate heat transfer and computational fluid dynamics to consider the conduction solids and the effects of wind speed and temperature in cold environments. The numerical analysis method of the surface heating element method was validated by comparing the experimental results of the heating coil method with the numerical analysis results (under the -30 ℃ conditions). The surface heating element method demonstrated significantly higher efficiency, ranging from 56.65-80.17%, depending on the conditions compared to the heating coil method. Moreover, even under extreme environmental conditions (-45 ℃), the surface heating element method satisfied anti-icing requirements. The surface heating element method is more efficient and economical than the heating coil method. However, proper heat flux calculation for environmental conditions is required to prevent excessive design.

Quality Enhancement of MIROS Wave Radar Data at Ieodo Ocean Research Station Using ANN

  • Donghyun Park;Kideok Do;Miyoung Yun;Jin-Yong Jeong
    • 한국해양공학회지
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    • 제38권3호
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    • pp.103-114
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    • 2024
  • Remote sensing wave observation data are crucial when analyzing ocean waves, the main external force of coastal disasters. Nevertheless, it has limitations in accuracy when used in low-wind environments. Therefore, this study collected the raw data from MIROS Wave and Current Radar (MWR) and wave radar at the Ieodo Ocean Research Station (IORS) and applied the optimal filter by combining filters provided by MIROS software. The data were validated by a comparison with South Jeju ocean buoy data. The results showed it maintained accuracy for significant wave height, but errors were observed in significant wave periods and extreme waves. Hence, this study used an artificial neural network (ANN) to improve these errors. The ANN was generalized by separating the data into training and test datasets through stratified sampling, and the optimal model structure was derived by adjusting the hyperparameters. The application of ANN effectively improved the accuracy in significant wave periods and high wave conditions. Consequently, this study reproduced past wave data by enhancing the reliability of the MWR, contributing to understanding wave generation and propagation in storm conditions, and improving the accuracy of wave prediction. On the other hand, errors persisted under high wave conditions because of wave shadow effects, necessitating more data collection and future research.

The measured contribution of whipping and springing on the fatigue and extreme loading of container vessels

  • Storhaug, Gaute
    • International Journal of Naval Architecture and Ocean Engineering
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    • 제6권4호
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    • pp.1096-1110
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    • 2014
  • Whipping/springing research started in the 50'ies. In the 60'ies inland water vessels design rules became stricter due to whipping/springing. The research during the 70-90'ies may be regarded as academic. In 2000 a large ore carrier was strengthened due to severe cracking from North Atlantic operation, and whipping/springing contributed to half of the fatigue damage. Measurement campaigns on blunt and slender vessels were initiated. A few blunt ships were designed to account for whipping/springing. Based on the measurements, the focus shifted from fatigue to extreme loading. In 2005 model tests of a 4,400 TEU container vessel included extreme whipping scenarios. In 2007 the 4400 TEU vessel MSC Napoli broke in two under similar conditions. In 2009 model tests of an 8,600 TEU container vessel container vessel included extreme whipping scenarios. In 2013 the 8,100 TEU vessel MOL COMFORT broke in two under similar conditions. Several classification societies have published voluntary guidelines, which have been used to include whipping/springing in the design of several container vessels. This paper covers results from model tests and full scale measurements used as background for the DNV Legacy guideline. Uncertainties are discussed and recommendations are given in order to obtain useful data. Whipping/springing is no longer academic.

대형 부유식 파력-해상풍력 복합발전 구조물의 극한환경 운동 성능에 대한 실험적 연구 (An Experimental Study on Dynamic Performance of Large Floating Wave-Offshore Hybrid Power Generation Platform in Extreme Conditions)

  • 김경환;홍장표;박세완;이강수;홍기용
    • 한국해양환경ㆍ에너지학회지
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    • 제19권1호
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    • pp.7-17
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    • 2016
  • 본 연구에서는 대형 부유식 파력-해상풍력 복합발전 구조물의 극한환경 운동 성능에 관한 실험적 연구를 다루고 있다. 대형 부유식 복합발전 구조물에 대한 운동 성능을 평가하기 위하여 1/50 축척비의 모형을 제작하였다. 그리고 설계된 계류선의 사양에 부합하는 계류선 모형을 제작하였고 자유감쇠시험 및 static pull-out 시험을 통하여 검증하였다. 주어진 구조물의 수심을 만족하기 위하여 계류선 테이블을 도입하고 환경조건에 계류판에 따른 환경조건을 확인하였다. 모형시험에서 규칙파 중 운동응답을 확인하고 파랑, 조류, 바람의 복합환경 하중을 적용하여 극한환경 운동성능을 해석하였다. 최대 운동 및, 가속도를 계측하여 운동 안전성을 판단하였고 최대 변위와 계류 하중도 선급기준에 따라 판단하였다. 이로부터 복합발전 구조물의 운동 특성에 대하여 토의하였다.

Validation of a 750 kW semi-submersible floating offshore wind turbine numerical model with model test data, part II: Model-II

  • Kim, Junbae;Shin, Hyunkyoung
    • International Journal of Naval Architecture and Ocean Engineering
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    • 제12권1호
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    • pp.213-225
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    • 2020
  • Floating Offshore Wind Turbines (FOWT) installed in the deep sea regions where stable and strong wind flows are abundant would have significantly improved energy production capacity. When designing FOWT, it is essential to understand the stability and motion performance of the floater. Water tank model tests are required to evaluate these aspects of performance. This paper describes a model test and numerical simulation for a 750-kW semi-submersible platform wind turbine model-II. In the previous model test, the 750-kW FOWT model-I suffered slamming phenomena from extreme wave conditions. Because of that, the platform freeboard of model-II was increased to mitigate the slamming load on the platform deck structure in extreme conditions. Also, the model-I pitch Response Amplitude Operators (RAO) of simulation had strong responses to the natural frequency region. Thus, the hub height of model-II was decreased to reduce the pitch resonance responses from the low-frequency response of the system. Like the model-I, 750-kW FOWT model-II was built with a 1/40 scale ratio. Furthermore, the experiments to evaluate the performance characteristics of the model-II wind turbine were executed at the same location and in the same environment conditions as were those of model-I. These tests included a free decay test, and tests of regular and irregular wave conditions. Both the experimental and simulation conditions considered the blade rotating effect due to the wind. The results of the model tests were compared with the numerical simulations of the FOWT using FAST (Fatigue, Aerodynamics, Structures, and Turbulence) code from the National Renewable Energy Laboratory (NREL).

해양관측용 부이의 설계 건전성 평가 - Part II: 계류시스템 구조건전성 평가 (Design of Oceanography Buoy - Part II: Mooring System)

  • 금동민;김태우;한대석;이원부;이제명
    • 한국해양공학회지
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    • 제23권1호
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    • pp.89-95
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    • 2009
  • The purpose of the present study was to evaluate the safety under extreme environmental conditions and the dynamic safety under service environment conditions, of oceanographic buoy mooring systems consisting of a variety of materials, including chain, wire rope, nylon rope, and polypropylene rope. For the static safety assessment of a mooring system, after the calculation of external forces and the division of a mooring system into finite elements, the numerical integral was conducted to yield the elemental static tension until satisfying the geometrical convergence condition. To evaluate the dynamic safety, various processes were considered, including data collection about the anticipated areas for mooring, a determination of the parameters for the interpretation, the interpretation of the dynamic characteristics based on an analytic equation that takes into account the heave motion effect of a buoy hull and a mooring system, and a fatigue analysis of the linear cumulative damage. Based on the analysis results, a supplementary proposal for a wire rope that has a fracture in an actual mooring area was established.

조석과 계절풍을 고려한 EST에 의한 동해연안의 극치해면 산정 (Estimation of Extreme Sea Levels with Consideration of Tide and Monsoon by Using EST at the East Coast)

  • 강주환;김양선;박선중;심재설
    • 한국해안·해양공학회논문집
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    • 제24권3호
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    • pp.210-216
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    • 2012
  • 극치해면 추정을 위해 EST기법을 동해연안에 적용하였다. 과거 60년간 발생한 TY급 태풍 51개에 의한 해일고를 ADCIRC모형으로 계산하여 트레이닝세트에 포함하였고, 태풍을 제외한 매년 발생하는 최대해일고를 계절풍에 의한 것으로 간주하여 계절풍에 따른 해일고도 응답벡터로 설정하였다. 조위조건을 입력벡터에 포함시켜 태풍시에는 고 저조 조건을 포함시켰으며 계절풍시에는 대 소조 조건을 입력벡터에 반영하였다. 이때 두 경우 모두 연주조를 감안하여 응답벡터를 작성하였다. 적용결과를 기존연구와 비교한 결과 정 등(2008)의 결과와 거의 일치하고 있어 본 방법의 적합성을 입증할 수 있었다.

부유식 파력발전장치용 계류선의 설계 및 안전성 검토에 관한 연구 (Investigation of Safety and Design of Mooring Lines for Floating Wave Energy Conversion)

  • 정동호;남보우;신승호;김현주;이호생;문덕수;송제하
    • 한국해양공학회지
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    • 제26권4호
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    • pp.77-85
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    • 2012
  • A study was performed on the design of a mooring line to maintain the position of a floating WEC (wave energy conversion) system. The procedure to design a mooring line is set up and the safety of the designed mooring system is evaluated using commercial software, Orcaflex. The characteristics curve for one line is analyzed to determine the properties and pretension of a mooring line. While considering the ocean environmental condition and importance of a floating WEC system, a multi-line layout is determined. A 4-point mooring system with 4 lines shows the instability in the yaw motion of the floating WEC system under a designed ocean environmental condition. The redesigned 4-point mooring system with 8 lines is found to be safe on the condition of a harsh ocean environment. The floating WEC system with the redesigned mooring system also shows stable motion in surge and pitch under operating conditions. From a parametric study on the mooring line length, the extreme value of the mooring line tension is found to be very sensitive to the pretension and length of mooring line. The results of this study can contribute to the establishment of a design procedure for mooring lines.