• Journal of Advanced Research in Ocean Engineering
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• 제1권4호
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• pp.227-238
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• 2015

The present work was an attempt to investigate the applicability of truncated mooring systems to KRISO's deep ocean engineering basin (DOEB) with ratios of 1:100, 1:60, and 1:50. The depth of the DOEB is 15 m. Therefore, the corresponding truncated depths for this study were equal to 1500 m, 900 m, and 750 m. The investigation focused on both the static and dynamic characteristics of the mooring system. It was shown, in a static pull-out test, that the restoring force of a FPSO vessel could be modified to a good level of agreement for all three truncation cases. However, when the radius of the mooring site was reduced according to the truncation factor, the surge motion response during a free-decay test showed a significant difference from the full-depth model. However, the reduction of this discrepancy was achieved by increasing the radius up to its maximum possible value while considering the size of the DOEB. Especially, in terms of the time period, the difference was reduced from 24.0 to 5.3 s for a truncation ratio of 1:100, 54.1 to 8.6 s for a truncation ratio of 1:60, and 31.7 to 3.9 s for a truncation ratio of 1:50. As a result, the study verified the applicability of the truncated mooring system to the DOEB, and therefore it could represent the full-depth mooring system relatively well in terms of the static and dynamic conditions.

• Journal of Advanced Research in Ocean Engineering
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• 제4권3호
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• pp.115-123
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• 2018

This study was carried using the new approach method to design appropriately the Loading Arm length and the alarm setting according to ship movements on Loading and Unloading marine Berth. The quasi-static mooring analysis was performed to estimate 110,000DWT ship's movements based on environmental conditions such as wind, current and wave. The mooring motion of the ship is very important to determine the loading arm scope, and in this case, the operation condition is performed on the ship without considering the damaged condition of the mooring line because the ship movement in case of damage is larger than intact, and all operations are stopped, the loading arm being released due to control system. From the result of mooring analysis, motion displacements, velocities and accelerations were simulated. They were used to simulate the maximum drifting speeds and distances. The maximum drifting speeds were checked to be satisfied within drifting speed limits. The total maximum drifting distances were simulated with alarm steps of the new approach method. Finally, the loading arm envelopes using the total maximum drifting distances were completed. Therefore, it was confirmed that the new approach method for loading arm envelopes and alarm settings was appropriate from the above results. In the future, it will be necessary to perform the further advanced dynamic mooring analysis instead of the quasi-static mooring analysis and to use the precise computer program analysis for various environments and ship movement conditions.

• 한국해양공학회지
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• 제26권2호
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• pp.48-57
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• 2012

This paper deals with numerical analyses in the context of estimations of hydrodynamic motions and dynamic loads for a floating type offshore platform using some exclusive simulation code such as code for the simulation of a floating type of offshore crane based on multi-body dynamics, along with the commercial code AQWA. Verifications of numerical models are carried out by comparing the RAO results from the simulation code. In the verification analyses, hydrodynamic motions are examined in the frequency domain for the floating type offshore platform according to the mooring lines. Both the hydrodynamic motions and dynamic loads are estimated for floating type offshore platforms equipped with the catenary type and taut mooring lines. A review and comparison are carried out for the numerically estimated results. The structural safety of the connection parts in an offshore structure such as a floating type offshore platform is one of the most important design criteria in view of fatigue life. The dynamic loads in the connecting area between a floating type offshore platform and its mooring lines are estimated in detail according to variations in the mechanical properties of the mooring lines. The dynamic tension load on the mooring lines is also estimated.

• International Journal of Ocean System Engineering
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• 제1권3호
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• pp.171-179
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• 2011

This paper presents the concept design procedure of a floating-type combined renewable energy platform based on hydrodynamic analyses and is focused on the fatigue design of taut-type mooring lines of the platform. Two types of combined renewable energy platforms are considered: a combination of wind turbine, wave turbine and photovoltaic energy plant and a combination of wind turbine, current turbine and photovoltaic energy plant. The basic configurations are conceptually determined from the understanding of floating offshore plants, while the main dimensions have been determined based on a hydrostatic calculation. Fully coupled hydrodynamic analyses have been carried out to identify the motion characteristics of the floating body and the tension histories of the mooring lines. The tension history is used for the fatigue life prediction based on the rain-flow cycle counting method. For the fatigue life prediction, tension life curves from API and the Palmgren-Miner rule are employed.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2013년도 춘계학술대회
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• pp.120-121
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• 2013

최근, 우리나라는 소득수준 향상, 교통여건 개선 등으로 여가활동 및 관광형태가 다양화되면서 육지 레저에서 해양 레저 활동이 증가하고 있다. 하지만 이런 여가활동을 수용할 수 있는 기반시설을 구축하고 있지만, 아직도 부족한 실정이다. 또한, 시설 구축 시 도입되는 기자재는 거의 전량을 수입하고 있으며 특히 마리나 구축 시 사용되는 긴장계류장치도 비슷한 상황이다. 따라서 이 논문에서는 에틸렌 프로필렌 고무와 아라미드섬유 등 재료를 이용하여 긴장계류장치를 구성하고 신뢰성 기반 강건 설계를 통해 국내 해양환경에 적합한 제품을 개발하여 해양레저문화 활성화와 산업발전에 이바지할 수 있을 거라고 생각한다.

• Ocean Systems Engineering
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• 제6권3호
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• pp.265-287
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• 2016

The change of the global performance of a turret-moored FPSO (Floating Production Storage Offloading) with DP (Dynamic Positioning) control is simulated, analyzed, and compared for two different internal turret location cases; bow and midship. Both collinear and non-collinear 100-yr GOM (Gulf of Mexico) storm environments and three cases (mooring-only, with DP position control, with DP position+heading control) are considered. The horizontal trajectory, 6DOF (degree of freedom) motions, fairlead mooring and riser tension, and fuel consumptions are compared. The PID (Proportional-Integral-Derivative) controller based on LQR (linear quadratic regulator) theory and the thrust-allocation algorithm which is based on the penalty optimization theory are implemented in the fully-coupled time-domain hull-mooring-riser-DP simulation program. Both in collinear and non-collinear 100-yr WWC (wind-wave-current) environments, the advantage of mid-ship turret is demonstrated by the significant reduction in heave at the turret location due to the minimal coupling with pitch mode, which is beneficial to mooring and riser design. However, in the non-collinear WWC environment, the mid-turret case exhibits unfavorable weathervaning characteristics, which can be reduced by employing DP position and heading controls as demonstrated in the present case studies. The present study also reveals the plausible cause of the failure of mid-turret Gryphon Alpha FPSO in milder environment than its survival condition.

• 한국해안·해양공학회논문집
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• 제27권5호
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• pp.364-371
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• 2015

본 연구는 험한 해양환경하에서 천해역에 떠 있는 부유체 해양양식장의 동적 거동 해석기법을 연구하기 위해 시도되었다. 본 연구의 내용은 양식장의 설치 위치를 연안이 아닌 근해지역으로 옮겼을 때 파도의 영향과 함께 계류라인이 해저면에 설치된 영향, 즉 해저면의 영향이 많은 영향을 미칠 것이라는 타 논문에서 발표된 사실을 밝히기 위해 수치해석 프로그램을 개발한 내용이며, 이를 통해 천해역에 설치된 계류라인과 해양 양식장을 모형화한 부유체 바지의 연성된 동적 응답해석을 수행할 때 해저면의 강성을 고려할 수 있는 프로그램을 확보하게 되었다.

• 대한조선학회논문집
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• 제33권4호
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• pp.162-174
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• 1996

내파성 연승식 양식시설은 케이블-부이-중량물 계류시스템으로 이루어졌다. 양식시설의 최적설계를 위해서는 계류선과 부이나 중량물 연결점에서 장력등의 추정이 필요하다. 그러나 계류선의 비선형적인 거동과 파 해류 등의 영향은 해석을 어렵게 한다. 본 논문에서는 여러 거지 부이-중량물을 갖는 케이블-부이-중량물 계류시스템에 대한 파라메트릭 연구를 통하여 동장력 변화 및 거동 변화 등을 알아보았다. 고유진동수 해석을 위하여 유한차분법을 도입하였으며, 비선형 유체항력은 선형화 되었다.

• 한국해양공학회지
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• 제22권5호
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• pp.69-74
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• 2008

This study performed a numerical simulation to predict the development of ship waves and their propagation in the shallow water region of Gunzang New Port and to examine the stability of taut line mooring at the sea wall using the design criteria. In order to predict the propagation of ship waves based on the speeds of various ships under complicated and shallow water depths, a computer model was constructed based on the Boussinesque equation with a fixed coordinate system. Additionally, an investigation if the stability was made by applying MOSES under the environmental loadings estimated by OCIMF.

• International Journal of Naval Architecture and Ocean Engineering
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• 제5권4호
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• pp.625-634
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• 2013

Energy is a direct restriction to the working life of an underwater mooring platform (UMP). In this paper, a vertical axis water turbine (VAWT) is designed to supply energy for UMPs. The VAWT has several controlled blades, which can be opened or closed by inside plunger pumps. Two-dimensional transient numerical studies are presented to determine the operating performance and power output of the turbine under low ocean current velocity. A standard k-${\varepsilon}$ turbulence model is used to perform the transient simulations. The influence of structural parameters, including foil section profile, foil chord length and rotor diameter, on the turbine performance are investigated over a range of tip-speed-ratios (TSRs). It was found that turbine with three unit length NACA0015 foils generated a maximum averaged coefficient of power, 0.1, at TSR = 2.