• 수산해양기술연구
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• 제40권4호
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• pp.360-366
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• 2004

침하식 가두리 시설의 안정성 평가를 위한 기초 단계로서 일방향 규칙파 중 2점 계류된 원통형 부체를 대상으로 부설 수심의 변화에 따른 부체의 동적 거동 및 계류삭에 작용하는 장력 산정에 관한 수치 계산을 수행하였다. 수치 계산 결과, 수면 상에 설치된 부체를 수면 아래의 약 1/2되는 수층까지 침하 시킨 경우 그것은 동적 거동과 파력은 초기 상태에 비해 각각 최대 50%와 77%까지 감소되어 시설물을 수중으로 침하 시키면 그것의 안정성 유지에 매우 효과적임을 확인할 수 있었다. 또한 부체의 전 후단 변위 및 계류삭에 작용하는 장력의 최대치는 부체의 고유 주기의 영향으로 인해 그것은 길이 d 에 대한 파장 ${\lambda}$의 비 즉, d/${\lambda}$가 약 0.66에서 나타났으며, 이와 같은 현상은 기존 수리 모형실험 결과와 비교적 잘 일치하였다. 그러나 본 수치 계산의 신뢰성 확인을 위해서는 수리 모형실험을 통해 부체의 고유 주기와 작용 파고에 대한 전 후단 변위 등에 대한 충분한 검토가 요구된다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제9권1호
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• pp.25-34
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• 2017

The concentric dual-buoy Wave Energy Converter (WEC), which consists of external buoy (hallow-cylinder) with toroidal appendage and cylindrical internal buoy within the moon-pool is suggested in this research and its performance in various wave conditions is studied. The Linear Electric Generator (LEG), consisting of a permanent magnet and coils, is used as a direct Power Take-Off (PTO) system. To maximize the electrical energy extracted from the PTO system, the relative heave motions between the dual buoys must be highly amplified by the multiple resonance phenomena of dual-buoy and internal-fluid motions. The high-performance range can be widened by distributing those natural frequencies with respect to the peak frequency of the wave spectrum. The performance of the newly developed dual-buoy WEC was measured throughout the systematic 1:5.95-model test in regular and irregular waves conducted in a wave tank at Seoul National University. The model-test results are also validated by an independently developed numerical method.

• 신재생에너지
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• 제9권4호
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• pp.25-31
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• 2013

This paper describes an electrical linear generator (IntELG) based on permanent magnets, containing heaving buoy, and its applications for the floating wave energy converters riding in parallel waves. The permanent magnets are integrated with the heaving buoy as a component and the integrated component is configured within the cylindrical IntELG to be filled with fluid. Thus, the IntELG can effectively be applied for the power-take-off of the floating wave energy converter riding in parallel waves. Typical applications are exampled with the Pelamis and Anaconda and they are investigated for the diversely redundant power source of nuclear power plant and the cooperation with submerged tunnel(s).

• 수산해양기술연구
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• 제53권4호
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• pp.309-316
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• 2017

In this paper, numerical modeling is conducted to analyze the tension of an anchor line by varying the size and drag coefficient of a buoy when the trapnet is influenced by the wave and the current simultaneously. A mass-spring model was used to analyze the behavior of trapnet underwater under the influence of waves and current. In the simulation of numerical model, wave height of 3, 4, 5 and 6 m, a period of 4.4 s, and the flow speed of 0.7 m/s were used for the wave and current condition. The drag coefficients of buoy were 0.8, 0.4 and 0.2, respectively. The size of buoy was 100, 50 and 25% based on the cylindrical buoy ($0.0311m^3$) used for swimming crab trap. The drag coefficient of the trapnet, the main model for numerical analysis, was obtained by a circular water channel experiment using a 6-component load cell. As a result of the simulation, the tension of the anchor line decreased proportional to buoy's drag coefficient and size; the higher the wave height, the greater the decrease rate of the tension. When the buoy drag coefficient and size decreased to one fourth, the tension of the anchor line decreased to a half and the tension of the anchor line was lower than the holding power of the anchor even at 6 m of wave height. Therefore, reducing the buoy drag coefficient and size appropriately reduces the trapnet load from the wave, which also reduces the possibility of trapnet loss.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2002년도 추계학술대회 논문집
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• pp.155-160
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• 2002

In this paper, a compliant buoy mooring system of a floating cylindrical structure in shallow water depth is studied experimentally. The compliant buoy mooring system consists of four buoys, vertical mooring legs and horizontal mooring lines. A series of model test were carried out at KRISO ocean engineering basin for various mooring parameters; line length, pretension of mooring leg and mooring layouts and environmental conditions; regular and irregular waves combined with current and wind. The mooring line tensions and 6-DOF motions of the floating structure were measured using water-proof load cells and 3 CCD camera system. The results of a series of model tests were discussed on nonlinear motion behaviors of the floating structure and characterisitics of cumulative distributions of mooring line peak tensions.

• 한국가시화정보학회지
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• 제9권3호
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• pp.51-58
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• 2011

The purpose of the study is to provide a foundation in predicting a maximum wave force when the ocean structure is laid out under breaking wave. Experiments were conducted with a down-scaled cylindrical model installed in a wave generating water channel. Maximum wave slopes were changed in regular wave condition by the wave breaker in the water channel. Cylinder's diameters were changed to 0.1m and 0.05m, respectively. Using the PIV results qualitative analyses were performed based upon the previous knowledge.

• International Journal of Naval Architecture and Ocean Engineering
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• 제6권4호
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• pp.813-825
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• 2014

To maximize electric power production using wave energy extractions from resonance power buoys, the maximum motion displacement spectra of the buoys can primarily be obtained under a given wave condition. In this study, wave spectra observed in shoaling water were formulated. Target resonance frequencies were established from the arithmetic means of modal frequency bands and the peak frequencies. The motion characteristics of the circular cylindrical power buoys with corresponding drafts were then calculated using numerical models without considering PTO damping force. Results showed that the heave motions of the power buoys in shoaling waters with insufficient drafts produced greater amplification effects than those in deep seas with sufficient drafts.