• Title/Summary/Keyword: 계류

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Study on Optimum Design of FPSO Spread Mooring System (FPSO 다점 계류 시스템의 최적 설계 연구)

  • Lim, Yu-Chang;Kim, Kyung-Su;Choung, Joon-Mo;Kim, Jae-Woo;Kim, Jin-Tae;Yeo, Seung-Hoon
    • Journal of Ocean Engineering and Technology
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    • v.23 no.6
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    • pp.61-66
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    • 2009
  • For a spread-moored FPSO (Floating Production, Storage, & Off-loading) subjected to environmental excitation from waves, current, and wind, a procedure to determine optimum length and stiffness of mooring lines is suggested using quasi-static frequency domain response analyses. Coupled relations between design parameters are closely examined. In consideration of this, optimized design parameters are proposed based on minimum weight condition. The initial design parameters for numerical analyses are calculated using the static catenary equation of mooring lines. It is demonstrated the line tension and vessel's offset are influenced by the mooring line length and stiffness. Accordingly it is suggested the optimum vessel's offset range should be determined considering line fatigue damage. The availability and limitation of the application of quasi-static analysis method for spread mooring system are explained by comparing the result of time domain analysis with one of frequency domain analysis.

Wave Responses and Ship Motions in a Harbor Excited by Long Waves(I) (항만내 파도응답과 계류선박의 운동해석(I))

  • I.H. Cho;Hang-S. Choi
    • Journal of the Society of Naval Architects of Korea
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    • v.29 no.2
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    • pp.38-47
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    • 1992
  • The motion response of a ship moored in a rectangular harbor excited by long waves has been studied theoretically and experimentally. Within the framework of potential theory, matched asymptotic expansion techniques are exployed to analyze the problem. The fluid domain is divided into the ocean and the harbor regions for the analysis of wave response in a harbor without ship. The wave responses in both the ocean and the harbor sides are solved first independently in terms of Green's functions, which are the solutions of the Helmholtz equation satisfying appropriate boundary conditions. Slender body approximations are used to obtain the velocity jumps across the ship, which are associated with the symmetric motion modes of the ship. Unknowns contained in each solution are finally determined by matching at an intermediate zone between two neighboring regions. Theoretical results predict the ship motion qualitatively well. The main source of quantitative discrepancies is presumably due to real fluid effects such as separation at the harbor entrance and friction on harbor boundaries.

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Seasonal Change Characteristics of Stream Water Quality in Planted Coniferous Forest (침엽수 인공림 계류수 수질의 계절변화 특성)

  • Kim, Jaehoon;Choi, Hyung Tae;Yoo, Jae Yun
    • Korean Journal of Environment and Ecology
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    • v.29 no.6
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    • pp.929-935
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    • 2015
  • This study was carried out to investigate pH, EC, solutes concentration and ANC characteristics in coniferous forest experiment watershed in Gyeonggi-do, Korea from 2005 to 2007. The average pH value was 6.87 and low at spring season due to deposition in crown. The average EC was $58.4{\mu}S/cm$ and was high at spring season due to high concentration of solutes. The cation and anion concentration was high at spring and fall season with low rainfall. When stream water quality was compared to different watershed, EC was relatively low due to high rainfall and $NO_3{^-}$ was high due to deposition and forest practice. pH and ANC was relatively constant at stream water

Large Slow-Drift Motions of a Floating Body in Slightly Modulated Waves (해상(海上)에 계류(繫留)된 부유체(浮遊體)의 표류운동(漂流運動) 해석(解析))

  • Dong-J.,Kim;Hang-S.,Choi
    • Bulletin of the Society of Naval Architects of Korea
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    • v.27 no.4
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    • pp.3-14
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    • 1990
  • For a moored body on the sea surface, incident waves with narrow-banded spectra excite the body oscillations of short and long periods. Since the period of slow oscillations can be as long as the natural period of the moored body in horizontal modes, resonance can occur and resulting large motions may cause significant strains in mooring cables. By using the perturbation method of multiple scales, the large slow motion can be analyzed without solving any second-order potentials explicitly. To the leading order, the flows associated with the fast and slow motions interact only parametrically and thus they can be studied separately. It is found that the slow motion strongly depends on the mooring stiffness. In particular, if the moring stiffness is considerably weak compared to the body inertia, the slow motion is highly amplified near resonance. It is also shown that the slow motion is associated with the generation of long waves.

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Experimental Study of Effect of Mooring Line Failure on Behavior of Turret-moored FPSO Ship (터렛 계류된 FPSO의 운동응답 및 계류선 손상 시 거동 특성에 대한 실험적 연구)

  • Hong, Jang-Pyo;Cho, Seok-Kyu;Seo, Jang-Hoon;Sung, Hong-Gun;Lee, Dong Yeop;Park, In Bo;Won, Young Uk;Choi, Sung Kwon;Kim, Dae-woong
    • Journal of Ocean Engineering and Technology
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    • v.29 no.3
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    • pp.231-240
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    • 2015
  • FPSO model tests of mooring line failure were carried out in the ocean basin at KRISO. The characteristics of the motions and mooring lines were investigated. The FPSO ship was moored using an internal turret and catenary mooring. The test model was 1/60 scale. The mooring lines were designed to satisfy the characteristics of the original mooring lines using the truncation method. The experiments were conducted under various environments: a safe wave, current and wind condition; single broken mooring line condition; and transient mode condition. The moment of the break was determined based on experimental test results. The results showed that the FPSO behavior and mooring line tensions were acceptable under the failure condition.