• Title/Summary/Keyword: 표류운동

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Nonlinear Motion Responses for A Moored Ship beside Quay (안벽에 계류된 선박에 대한 비선형 운동응답)

  • Lee, Ho-Yooung;Lim, Choon-Gyu;Lew, Jae-Moon;Chun, In-Sik
    • Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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    • 2003.05a
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    • pp.172-178
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    • 2003
  • As a typoon gets into harbour, a moored ships shows erratic motions and even mooring line failures is occurred. Such troubles may be caused by harbour resonance phenomena, result in large motion amplitudes at law frequency, which is closed to the natural frequency of the moored ship. The nonlinear motions of a moored ship beside quay are simulated under external forces due to wave, current including mooring forces in time domain. The forces due to waves are obtained from source and dipole distribution method in the frequency domain. The current forces are calculated by using slow motion maneuvering equation in the horizontal plane. The wind forces are calculated from emperical formula of ABS and the mooring forces of ropes and fenders are modeled as linear spring.

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Nonlinear Motion Analysis of FPSO and Shuttle Tanker in a Tandem Configuration (탠덤 배치된 FPSO와 셔틀탱커의 비선형 운동 해석)

  • Lim, Choon-Gyu;Lee, Ho-Young;Shin, Hyung-Young
    • Journal of the Society of Naval Architects of Korea
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    • v.43 no.5 s.149
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    • pp.560-567
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    • 2006
  • FPSO and shuttle tanker are connected to each other by a mooring hawser and a loading hose through which cargo oil is off-loaded. Even in mild sea-state. environmental loads can cause unstable large drift motions between two vessels in tandem off-loading operations, which may result in collision incidents. Accordingly. the analysis on the relative motion between two vessels due to the environmental loads should be investigated in initial design stage. In this study, the low speed maneuvering equation is employed to simulate nonlinear motions of FPSO and shuttle tanker. Low frequency wave drift forces including hydrodynamic interactions between two vessels are evaluated by near field approaches. Current loads are determined by mathematical model of MMG and wind loads are calculated by employing the wind spectrum according to the guidelines of API-RP2A. Mooring forces produced by turret mooring lines and a flexible hawser are modeled quasi-statically by catenary equations. The effect of environmental loads that affect nonlinear motion is investigated through variation in their magnitudes and the nonlinear motions between FPSO and shuttle tanker are simulated under wave, current and wind in time domain.

Ecotoxicological Study of Gammarus sobaegensis by pH Depression in Artificial Channels - Drift behavior - (인공수로에서 산성화 영향에 따른 소백옆새우(Gammarus sobaegensis)의 생태독성학적 연구 - 표류행동을 중심으로 -)

  • Park, Jung-Ho;Cho, Dong-Hyun;Jung, Geun
    • Korean Journal of Environmental Biology
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    • v.18 no.1
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    • pp.153-161
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    • 2000
  • This study was carried out to examine the drift of Gammarus sobaegensis by acid stress as pH depression in Oweol creek from April 1996 to October 1996. The behavioral drifting was revealed to the characteristics of G. sobaegensis that is tend to increase as acid stress. And, tolerance level of G. sobaegensis to pH depression was different among the size classes. Individuals belong to small to medium size classes were weak in lower pH. Pattern of response in G. sobaegensis has a lower tolerance to acid stress at below pH 4.0 than above pH 5.0 in the artificial channel and show the possibility as an effective aquatic ecotoxicity test organism. The result of analysis of variance, water temperature (F-ratio : 66.596, p< 0.0005) and the size classes (F-ratio : 71.386, p< 0.0005) except pH level (F-ratio : 353.415, p<0.0005) were showed to the major factor for drift behavior by acid depression. [Gammarus, pH, Drift, Acid stress, Ecotoxicity test].

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An Effect of the Eddy Intrusive Transport Variations Across the Shelfbreak on the Korea Strait and the Yellow sea Part 1 : Barotropic Model Study (대륙붕사면에서의 에디 유입에 의한 해수수송량 변화가 대한해협 및 황해에 미치는 영향 제1부 : 순압 모델 연구)

  • YOO, KWANG WOO;OH, IM SANG
    • 한국해양학회지
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    • v.28 no.4
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    • pp.281-291
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    • 1993
  • A time-dependent primitive two0dimensional calculation is conducted to investigate the variations of Vol. transport onto the Yellow Sea and the Korea Strait with real bathymetries and to tract the Lagrangian movement of water particles. A series of experiment of the barotropic Kuroshio intrusions shows that the eddy induced branching of Kuroshio has sufficient intensity as to modify the continental shelf circulation. This intrusion seems to be one of the important forcing terms such as winds. tides and buoyancy that can also affect the dynamics in the region of the continental shelf. Transport variations across the shelfbreak due to the branching of Kuroshio which come particularly from the southwest of the Kyushu Island, have a strong relationship with the transport variations across the Korea Strait and in the southern area of the Yellow sea. The particle trajectories of the model results are well agreed with the trajectories of satellite tracking drifters obtained by one of the WOCE/TOGA program except the longer travel time period in the present model.

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Analysis on the Pattern of Dragging Anchor in Actual Ship (실선 계측에 의한 주묘패턴 분석에 관한 연구)

  • Jung, Chang-Hyun;Kong, Gil-Young;Bae, Byung-Deug;Lee, Yun-Sok
    • Journal of Navigation and Port Research
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    • v.33 no.8
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    • pp.505-511
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    • 2009
  • Vessels on anchoring are frequently dragged due to the increased area of wind pressure by enlargement of ship's size and sudden gust of winds in recent years. In the view point of the ship's navigators, the proper measurements corresponding to the dragging of anchor should be taken into account concerned about the time for the occurring of dragging by the external forces such as wind and wave, the pattern and speed of dragging and the possibility of collisions with any other vessels or obstacles. In this paper, it was examined the actual dragging anchor in T.S. HANBADA due to the wind and waves. From this case, it was found the critical external forces by which she was begun to dragged comparing the force by the wind, frictional resistance, drifting force and ship motion moment with the holding power. Also, through the analysis of the dragging pattern, it was known the alteration range of heading angle, swinging width and dragging speed etc.

Current Effect on the Motion and Drift Force of Cylinders Floating in Waves (주상체(柱狀體)의 운동(運動) 및 표류력(漂流力)에 미치는 해류(海流)의 영향(影響))

  • Sei-Chang,Lee
    • Bulletin of the Society of Naval Architects of Korea
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    • v.23 no.4
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    • pp.25-34
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    • 1986
  • A two-dimensional linear method has been developed for the motion and the second-order steady force arising from the hydrodynamic coupling between waves and currents in the presence of a body of arbitrary shape. Interaction between the incident wave and current in the absence of the body lies in the realm beyond our interest. A Fredholm integral equation of the second kind is employed in association with the Haskind's potential for a steadily moving source of pulsating strength located in or below the free surface. The numerical calculations at the preliminary stage showed a significant fluctuation of the hydrodynamic forces on the surface-piercing body. The problem is approximately solved by using the asymptotic Green function for $U^2{\rightarrow}0$. The original Green function, however, is applied for the fully submerged body. Numerical calculations are made for a submerged and for a half-immersed circular cylinder and extensively for the mid-ship section of a Lewis-form. Some of the results are compared with other analytical results without any available experimental data. The current has strong influence on roll motion near resonance. When the current opposes the waves, the roll response are generally negligible in the low frequency region. The current has strong influence on roll motion near resonance. When the current opposes the wave, the roll response decreases. When the current and wave come from the same direction, the roll response increases significantly, as the current speed increases. The mean drift forces and moment on the submerged body are more affected by current than those on the semi-immersed circular cylinder or on the ship-like section in the encounter frequency domain.

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Eddy Diffusion in Coastal Seas: Observation and Fractal Diffusion Modelling (연안역와동확산: 관측 및 프랙탈 확산 모델링)

  • 이문진;강용균
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.9 no.3
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    • pp.115-124
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    • 1997
  • We measured the variance of eddy diffusion and associated ‘diffusion coefficients’ in coastal regions of Korea by observing the separation distances among multiple drifters deployed simultaneously at the same initial position. The variance of eddy diffusion was found to be proportional to $t^m$, where t is the time and m is a non-integer scaling exponent between 1.5 and 3.5. The observed scaling exponent of eddy diffusion cannot be reproduced by diffusion models employing constant eddy diffusivity. In this study, we applied fractal theory in simulating exponential increase of variance of eddy diffusion. We employed the fGn(fractional Gaussian noise) as a ‘modified’ random walks corresponding to the oceanic eddy diffusion. The variance of eddy diffusion, which corresponds to the fBm(fractional Brown motion) of our diffusion model, is proportional to $t^{2H}$, where H is Hurst scaling exponent. The temporal increase of the variance. with scaling exponent between 1 and 2, was successfully reproduced by our fractal diffusion model. However, our model cannot reproduce scaling exponent greater than 2. The scaling exponents greater than 2 are associated with the velocity shear of the mean flow.

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