• 한국해안·해양공학회논문집
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• 제22권5호
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• pp.306-315
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• 2010

대규모 해상풍력 개발이 예상되고 있는 가운데, 이러한 대규모 단지개발을 위해서는 사전 환경영향평가가 매우 중요하다. 해상풍력단지 개발 후보지 중 하나인 전북 위도 부근 해역에서의 파랑 관측 자료를 토대로 파랑추산 모형을 검증하고, 해상풍력터빈을 위한 직경 5 m의 모노파일 기초 35기 설치시 파랑 거동에 미치는 영향을 검토하였다. 파랑추산 모형의 유의파고 계산 결과, 관측자료와의 RMS 오차가 0.35 m 정도로 재현성이 우수함을 확인하였으며, 터빈이 설치되는 경우 파고 감쇠율이 1% 미만으로 영향이 거의 없음을 확인할 수 있었다.

• 한국해양학회지
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• 제15권1호
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• pp.1-7
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• 1980

The results of measurements of shear current induced in water by wind in wind wave tunnel are presented briefly. The shear current distributions are found to fit reasonably well an exponentiall form. This form was used to estimate surface velocity and boundary layer thickness used in stability analysis. An analysis of hydrodynamic stability of the shear current was carried out, using a broken line as an approximate profile, to see the stability as a possible mechanism of wind wave generation. Comparison between experimental results and theoretical ones shows that there exists a large discrepancy particularly in phase velocity and hydrodynamic instability of the shear current seems not to be the basic mechanism of wind wave generation.

• International Journal of Naval Architecture and Ocean Engineering
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• 제10권1호
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• pp.9-20
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• 2018

Due to integrated stochastic wind and wave loads, the supporting platform of a Floating Offshore Wind Turbine (FOWT) has to bear six Degrees of Freedom (DOF) motion, which makes the random cyclic loads acting on the structural components, for instance the tower base, more complicated than those on bottom-fixed or land-based wind turbines. These cyclic loads may cause unexpected fatigue damages on a FOWT. This paper presents a study on short-term fatigue damage at the tower base of a 5 MW FOWT with a spar-type platform. Fully coupled time-domain simulations code FAST is used and realistic environment conditions are considered to obtain the loads and structural stresses at the tower base. Then the cumulative fatigue damage is calculated based on rainflow counting method and Miner's rule. Moreover, the effects of the simulation length, the wind-wave misalignment, the wind-only condition and the wave-only condition on the fatigue damage are investigated. It is found that the wind and wave induced loads affect the tower base's axial stress separately and in a decoupled way, and the wave-induced fatigue damage is greater than that induced by the wind loads. Under the environment conditions with rated wind speed, the tower base experiences the highest fatigue damage when the joint probability of the wind and wave is included in the calculation. Moreover, it is also found that 1 h simulation length is sufficient to give an appropriate fatigue damage estimated life for FOWT.

• 한국지구과학회지
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• 제26권3호
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• pp.240-252
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• 2005

한반도 주변 해역의 5개 지점(덕적도, 칠발도, 거문도, 거제도, 동해 정점)에서 관측된 기상청의 해양 기상 관측 부이 자료를 이용하여 각 해역에서 바람과 파도의 관계를 분석하였다. 전반적으로는 서해 정점에서는 파도가 바람의 영향을 가장 많이 받고 남해 정점에서는 파도가 바람의 영향을 가장 적게 받으며 동해 정점에서는 그 중간이며 각 정점별 특징은 다음과 같다. 칠발도에서는 풍속이 강한 겨울철의 주 풍향인 북서방향으로 바다가 트여있고 얕은 수심에 의한 여울효과로 가장 높은 파고가 발달하며 풍향과 파향이 다른 정점에 비해서 가장 잘 일치한다. 이에 비해 덕적도는 북서방향이 황해도에 의해 막혀 있기 때문에 취송거리가 제한되어 겨울철에 충분히 발달한 파도가 생기지 않는다. 이러한 취송거리의 제한은 남해 정점에서 더 크다. 북풍이 우세한 남해의 두 정점에서는 북쪽의 육지 때문에 파도의 발달이 제한되어 바람이 강해도 파고는 거의 높아지지 않는다. 남해 정점에서는 어느 방향에서 바람이 불든지 모든 파향의 파가 고르게 유입되며 그 중 우세한 파향은 항상 동중국해에서 유입되는 방향이다. 그 방향은 거문도와 거제도에서 각각 남쪽 방향과 남서 방향이며 이 방향으로는 바람이 약할 때도 파도가 유입된다. 동해 정점에서는 수심이 깊어 파도가 크게 발달하지만 풍향과 파향이 일치하지 않는 경우가 많아 파고의 발달이 칠발도에서 보다는 낮다. 이와 같이 풍속과 더불어 풍향이 파랑발달에 중요한 이유는 풍향에 의해 취송거리가 결정되기 때문이다. 덕적도와 칠발도에서 풍향이 변하지 않고 오래 지속되는 경우를 보면 파향이 풍향과 일치하며 파고는 최대풍속 후에 최대파고가 나타나는 반응시간이 길수록 커지는 것을 볼 수 있다. 그러나 풍향과 파향이 일치하지 않는 동해 정점의 경우에서는 풍속이 크고 반응시간이 길어도 파고가 서해 정점에서와 같이 많이 높아지지는 않는다. 이상의 결과는 풍속이 클수록, 취송거리가 길수록, 지속시간이 길수록 파고가 크게 발달하는 일반적인 경향과 더불어 각 정점별로는 육지와 바다의 방향, 해저지형, 주변해역의 규모 등의 환경조건에 의해 바람에 의한 파도의 발달율이 달라지는 것을 보여준다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 추계학술대회 초록집
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• pp.184.1-184.1
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• 2010

Floating wind turbines have been suggested as a feasible solution for going further offshore into deeper waters. However, floating platforms cause additional unsteady motions induced by wind and wave conditions, so that it is difficult to predict annual energy output of wind turbines by using conventional power prediction method. That is because sectional inflow condition on a rotor plane is varied by unsteady motion of floating platforms. Therefore, aerodynamic simulation using Vortex Lattice Method(VLM) were used to investigate the influence of motion on the aerodynamic performance of a floating offshore wind turbine. Simulation with individual motion of offshore platform were compared to the case of onshore platform and carried out according to the wave height and the wave angular frequency.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2006년도 추계학술대회
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• pp.305-306
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• 2006

This paper introduces a radio-wave interference assessment of wind turbines that were planned to be installed at Homi-Cape in Pohang region where wind resource has been evaluated worthwhile developing a wind farm. In that area, AM radio station with two antennas and a harbor radar facility are located so that radio-wave coupling is inevitable if the wind farm is designed without considering radio-wave environmental impact. A low-frequency analysis using MoM (Method of Moment) is used to examine interference effect caused by wind turbines and an optimal layout minimizes coupling effect is presented.

• 한국해양공학회지
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• 제36권6호
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• pp.390-402
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• 2022

Offshore wind energy has become a major energy source, and various studies are underway to increase the economic feasibility of floating offshore wind turbines (FOWT). In this study, the characteristics of wave-induced motion of a combined wind-wave energy platform were analyzed to reduce the variability of energy extraction. A user subroutine was developed, and numerical analysis was performed in connection with the ANSYS-AQWA hydrodynamic program in the time domain. A platform combining the TLP-type FOWT and the Wavestar-type wave energy converter (WEC) was proposed. Each motion response of the platform on the second-order wave load, the effect of WEC attachment and Power take-off (PTO) force were analyzed. The mooring line tension according to the installation location was also analyzed. The vertical motion of a single FOWT was increased approximately three times due to the second-order sum-frequency wave load. The PTO force of the WEC played as a vertical motion damper for the combined platform. The tension of the mooring lines in front of the incident wave direction was dominantly affected by the pitch of the platform, and the mooring lines located at the side of the platform were mainly affected by the heave of the platform.

• Ocean Systems Engineering
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• 제13권1호
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• pp.21-41
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• 2023

Decarbonization and energy transition can be considered as a main concern even for the oil industry. One of the initiatives to reduce emissions under studies considers the use of renewable energy as a complimentary supply of electric energy of the production platforms. Wind energy has a higher TRL (Technology Readiness Level) than other types of energy converters and has been considered in these studies. However, other types of renewable energy have potential to be used and hybrid concepts considering wind platforms can help to push the technological development of other types of energy converters and improve their efficiency. In this article, a preliminary hydrodynamic assessment of a new concept of hybrid wind and wave energy conversion platform was performed, in order to evaluate the potential of wave power extraction. A multiple OWCs (Oscillating Water Column) WEC (Wave Energy Converter) design was adopted for the analysis and some simplifications were adopted to permit using a frequency domain approach to evaluate the mean wave power estimation for the location. Other strategies were used in the OWC design to create resonance in the sea energy range to try to maximize the potential power to be extracted, with good results.

• Structural Engineering and Mechanics
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• 제57권5호
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• pp.951-968
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• 2016

Long-span cross-strait bridges extending into deep-sea waters are exposed to complex marine environments. During the construction stage, the flexible freestanding bridge towers are more vulnerable to environmental loads imposed by wind and wave loads. This paper presents an experimental investigation on the dynamic responses of a 389-m-high freestanding bridge tower model in a test facility with a wind tunnel and a wave flume. An elastic bridge model with a geometric scale of 1:150 was designed based on Froude similarity and was tested under wind-only, wave-only and wind-wave combined conditions. The dynamic responses obtained from the tests indicate that large deformation under resonant sea states could be a structural challenge. The dominant role of the wind loads and the wave loads change according to the sea states. The joint wind and wave loads have complex effects on the dynamic responses of the structure, depending on the approaching direction angle and the fluid-induced vibration mechanisms of the waves and wind.

• Wind and Structures
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• 제10권5호
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• pp.401-420
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• 2007

Field measurements of the wind-induced response of two residential reinforced concrete buildings, among the tallest in the world, have been performed during two typhoons. Natural periods and damping values have been determined and compared with other field measurements and empirical predictors. Suitable and common empirical predictors of natural period and structural damping have been obtained that describe the trend of tall, reinforced concrete buildings whose structural vibrations have been measured in the collection of studies in Hong Kong compiled by the authors. This data is especially important as the amount of information known about the dynamic parameters of buildings of these heights is limited. Effects of the variation of the natural period and damping values on the alongwind response of a tall building for serviceability-level wind conditions have been profiled using the gust response factor approach. When using this approach on these two buildings, the often overestimated natural periods and structural damping values suggested by empirical predictors tended to offset each other. Gust response factors calculated using the natural periods and structural damping values measured in the field were smaller than if calculated using design-stage values.