• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 춘계학술대회 논문집
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• pp.630-631
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• 2009

Recent developments such as concern over global warming, depletion of fossil fuels and increase in energy demands by the increasing world population has eventually lead to mass production of electricity using renewable sources. Apart from wind and solar, ocean holds tremendous amount of untapped energy in forms such as geothermal vents, tides and waves. The current study looks at generating power using waves and the focus is on the primary energy conversion (first stage conversion) of incoming waves for two different models. Observation of flow characteristics, pressure and the velocity in the augmentation channel as well as the front guide nozzle are presented in the paper. A numerical wave tank was utilized to generate waves of desired properties and later the turbine section was integrated. The augmentation channel consisted of a front nozzle, rear nozzle and an internal fluid region representing the turbine housing. The analysis was performed using the commercial CFD code.

• 천문학회보
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• 제37권2호
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• pp.117.2-117.2
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• 2012

It is generally accepted that sudden compressions of the magnetosphere cause electromagnetic ion cyclotron (EMIC) wave growth by increasing the proton temperature anisotropy. These compression-associated EMIC waves are expected to be on higher latitudes (i.e., higher-L regions close to the magnetopause). In this study we examine Pc1 pulsations, which are believed to be generated by the EMIC instability, observed at subauroral latitude near the nominal plasmapause when the magnetosphere is suddenly compressed by solar wind dynamic pressure variations, using induction magnetometer data obtained from Athabasca, Canada (geomagnetic latitude = 61.7 N, L ~ 4.5). We identified 9 compression-associated Pc1 waves with frequencies of ~0.5-2.0 Hz. The wave activity appears in the horizontal H (positive north) and D (positive eastward) components. All of events show low coherence between H and D components. This indicates that the Pc1 pulsations in H and D oscillate with a different frequency. Thus, we cannot determine the polarization state of the waves. We will discuss the occurrence location of compression-associated Pc1 pulsations, their spectral structure, and wave properties.

• 대한조선학회논문집
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• 제43권1호
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• pp.1-14
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• 2006

To improve maritime safety, it is very important not only to make safer design and operation but also to do proper response in case of maritime casualty. The large-scaled casualties will be caused by loss of structural strength and stability due to the progressive flooding and enlargement of damage by the effect of waves and wind. To prevent foundering and structural failure, the prediction of ship motion behavior of damaged ship in wave is necessary. This paper describes the motion behavior of damaged ship in waves through theoretical and experimental studies. A time domain theoretical model of damaged ship motions and accidental flooding, which can be applied to any type of ship or arrangement and considers the effects of flooding of compartments, has been developed. The model tests have been carried out in regular and irregular waves with different wave heights and directions in ship motion basin. Those were performed for three different damaged conditions such as engine room bottom damage, side shell damage and bow visor damage of a Ro-Ro ship. Comparison of theoretical and experimental results was performed.

• 한국정보기술학회논문지
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• 제17권9호
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• pp.11-17
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• 2019

최근 들어 동해안에서 너울성 파도에 의한 손실이 빈번히 발생하고 있다. 너울성 파도는 다양한 요인들이 결합되어 발생하기 때문에 예측이 어렵다. 본 연구에서는 머신러닝 기술에 기초하여 동해안에서 너울성 파도의 발생을 예측하는 모델을 제안하였다. 모델 개발을 위해 포항 신항의 하역중단 데이터 및 신항 부근의 기압, 풍속, 풍향, 수온 등의 기상자료를 수집하였다. 수집한 데이터로부터 너울발생에 중요한 영향을 미치는 변수들을 선별하였으며, 모델 개발을 위해 다양한 머신러닝 예측 알고리즘들을 테스트 하였다. 그 결과 조위, 수온, 기압이 너울 발생 예측을 위한 주요 변수로 확인이 되었고, Random Forest 모델이 가장 우수한 성능을 보였으며. 모델의 예측 정확도는 88.6%이다.

• 한국수산과학회지
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• 제10권3호
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• pp.179-187
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• 1977

서귀포 연안에 인공어초를 설치하여 어군의 형태와 어군의 위집에 관한 연구에서 아래와 같은 결과를 얻었다. 1. 어초설치 해역의 15.28cm/sec였고 유향은 WSW가 $20.5\%$에 대한 취송류는 최고유속이 15.28cm/sec 유향은 WSW가 $20.5\%$였다. 2. 흐름과 파에 의한 원형수하형어초의 유체저항은 약 890kg이 최대였고, 어초에 부착된 멍의 중량은 1,200kg로서 고정력이 충분하였다. 3. 파라슈트어초에 대한 최대저항은 전개용 자료가 약하여 유지되지 못하였다. 4. 제주도 근해산 중요어류 53종중 인공어초에 위집한 어종은 16종이었고 어획조성비는 참돔 $23\%, 볼라 $13\%, 보리멸 $11\%$, 우럭볼락 $7\%$, 주치 $6\%$이고 잠수관찰에서 어초의 중층부에 많은 치어가 위집된 것을 확인하였다.

• 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.

• 한국해안·해양공학회논문집
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• 제25권6호
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• pp.349-356
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• 2013

본 연구에서는 만 또는 도서지역과 같이 지형적으로 차폐되어 외해로부터 직접적인 파랑전파가 어렵고 바람에 의해 발달된 파랑의 영향이 클 것으로 판단되는 지역에 사용되는 기존 만내설계파 모델의 문제점을 분석하고 개선방안을 검토하였다. 기존 만내설계파 모델은 바람을 고려할 수 있고 타 모델에 비해 복잡한 지형에도 비교적 간편하게 사용할 수 있는 장점을 지니는 반면 인근 대형 구조물 또는 지형에 의한 파랑의 회절 및 반사 등의 고려가 곤란하다. 기존모델의 단점을 극복하기 위해 회절 및 반사각, 수심변화 등의 고려가 가능한 개량된 만내설계파 모델을 현지에 적용하고 기존 모델과 비교 검토한 결과 구조물 주변에서 설계파고의 값에 신뢰성이 향상되는 것을 확인하였다. 따라서 개선된 만내설계파 모델은 차폐되어 있는 해역에서 항만 구조물 설계 시 기존의 방법에 비해 보다 고정도의 설계파를 산정하는 방법으로서 이용될 수 있을 것으로 판단된다.

• 한국해양공학회지
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• 제18권6호
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• pp.8-15
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• 2004

Wave power distribution is investigated to determine the optimal sites for wave power generation at Jeju sea which has the highest wave energy density in the Korean coastal waters. The spatial and seasonal variation of wave power per unit length is calculated in the Jeju sea area based on the monthly mean wave data from 1979 to 2002 which is produced by the SWAN wave model simulation in prior research. The selected favorable locations for wave power generation are compared in terms of magnitude of wave energy density and distribution characteristics of wave parameters. The results suggest that Chagui-Do is the most optimal site for wave power generation in the Jeju sea. The seasonal distribution of wave energy density reveals that the highest wave energy density occurs in the northwest sea in the winter and it is dominated by wind waves, while the second highest one happens at south sea in the summer and it is dominated by a swell sea. The annual average of wave energy density shows that it gradually increases from east to west of the Jeju sea. At Chagui-Do, the energy density of the sea swell sea is relatively uniform while the energy density of the wind waves is variable and strong in the winter.

• 한국해안·해양공학회논문집
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• 제26권2호
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• pp.81-95
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• 2014

본 연구에서는 동해안의 너울성파랑을 예 경보하기 위한 기초단계로 동해 폭풍파랑의 특성을 분석하고, 수정 WAM모형을 이용해 이를 재현하였다. 본 연구의 파랑관측자료분석 결과에 의하면, 동해 심해역의 파랑은 NE계열의 파랑이 지배적이었으나, 폭풍파랑은 N계열의 출현율이 가장 높은 것으로 나타났다. 이외에 N 및 NNE 계열의 폭풍파랑에 대한 유의파고는 NE 계열 폭풍파랑의 유의파고보다 더 큰 것으로 분석되었다. 그러나 긴 취송거리에 의하여 유의파주기는 NE계열의 폭풍파랑의 유의파주기가 N또는 NNE계열의 유의파주기보다 크게 나타났다. 효과적인 동해역 폭풍파랑 예 경보를 위해 5분의 공간격자간격에 기반한 수치모의실험을 구축하고, 이를 2013년의 주요 폭풍파랑에 적용하였다. 본 연구의 수치모의실험 결과를 심해 및 천해 파랑측정 자료와 비교한 결과 전반적으로 잘 일치하였다. 그러나 천해역의 경우 수심 및 바람장의 해상도가 부족하여 수치모의의 정확도가 약간 떨어지는 것을 알 수 있었다. 본 연구진이 개발한 수정 WAM모델은 음해법을 사용하여 기존 WAM모형보다 10배 정도 빠르게 동해 폭풍파랑의 수치모의 계산을 수행할 수 있었다.

• Ocean Science Journal
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• 제41권4호
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• pp.245-254
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• 2006

Long term wave climate of both extreme wave and operational wave height is essential for planning and designing coastal structures. Since the field wave data for the waters around Korean peninsula is not enough to provide reliable wave statistics, the wave climate information has been generated by means of long-term wave hindcasting using available meteorological data. Basic data base of hindcasted wave parameters such as significant wave height, peak period and direction has been established continuously for the period of 25 years starting from 1979 and for major 106 typhoons for the past 53 years since 1951 for each grid point of the North East Asia Regional Seas with grid size of 18 km. Wind field reanalyzed by European Center for Midrange Weather Forecasts (ECMWF) was used for the simulation of waves for the extra-tropical storms, while wind field calculated by typhoon wind model with typhoon parameters carefully analyzed using most of the available data was used for the simulation of typhoon waves. Design wave heights for the return period of 10, 20, 30, 50 and 100 years for 16 directions at each grid point have been estimated by means of extreme wave analysis using the wave simulation data. As in conventional methodsi of design criteria estimation, it is assumed that the climate is stationary and the statistics and extreme analysis using the long-term hindcasting data are used in the statistical prediction for the future. The method of extreme statistical analysis in handling the extreme vents like typhoon Maemi in 2003 was evaluated for more stable results of design wave height estimation for the return periods of 30-50 years for the cost effective construction of coastal structures.