• Title/Summary/Keyword: Extreme wave

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Characteristics of Spread Parameter of the Extreme Wave Height Distribution around Korean Marginal Seas (한국 연안 극치 파고 분포의 확산모수 특성)

  • Jeong, Shin-Taek;Kim, Jeong-Dae;Ko, Dong-Hui;Kim, Tae-Heon
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.21 no.6
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    • pp.480-494
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    • 2009
  • Long term extreme wave data are essential for planning and designing coastal structures. Since the availability of the field data for the waters around Korean peninsula is limited to provide a reliable wave statistics, the wave climate information has been generated by means of long-term wave hindcasting using available meteorological data. KORDI(2005) has proposed extreme wave data at 106 stations off the Korean coast from 1979 to 2003. In this paper, extreme data sets of wave(KORDI, 2005) have been analyzed for best-fitting distribution functions, for which the spread parameter proposed by Goda(2004) is evaluated. The calculated values of the spread parameter are in good agreement with the values based on method of moment for parameter estimation. However, the spread parameter of extreme wave data has a representative value ranging from about 1.0 to 2.8 which is larger than some foreign coastal waters, it is necessary to review deep water design wave.

Stochastic procedures for extreme wave induced responses in flexible ships

  • Jensen, Jorgen Juncher;Andersen, Ingrid Marie Vincent;Seng, Sopheak
    • International Journal of Naval Architecture and Ocean Engineering
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    • v.6 no.4
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    • pp.1148-1159
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    • 2014
  • Different procedures for estimation of the extreme global wave hydroelastic responses in ships are discussed. Firstly, stochastic procedures for application in detailed numerical studies (CFD) are outlined. The use of the First Order Reliability Method (FORM) to generate critical wave episodes of short duration, less than 1 minute, with prescribed probability content is discussed for use in extreme response predictions including hydroelastic behaviour and slamming load events. The possibility of combining FORM results with Monte Carlo simulations is discussed for faster but still very accurate estimation of extreme responses. Secondly, stochastic procedures using measured time series of responses as input are considered. The Peak-over-Threshold procedure and the Weibull fitting are applied and discussed for the extreme value predictions including possible corrections for clustering effects.

Theoretical Study on the Generation of Directional Extreme Waves (다방향 극한파 생성의 이론적 연구)

  • Key-Yong Hong;Shuxue Liu;Seok-Won Hong
    • Journal of the Society of Naval Architects of Korea
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    • v.39 no.1
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    • pp.38-48
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    • 2002
  • Theoretical development to generate the directional extreme waves in model basin is established based on wave focusing method. The effects of associated parameters, such as the directional range, frequency width, and center frequency, are investigated in terms of wave focusing efficiency. The two different spectral models of constant wave amplitude and constant wave slope are applied to control the wave characteristics. The wave packets simulated by theory are compared with numerical results based on Boussinesq equation and FEM. Both controls of direction and frequency spectrum are essential to focus directional waves effectively. It is noticed that wave focusing ability depends on the frequency bandwidth of spectrum rather than center frequency, and both spectral models with same parameters result in the equivalent efficiency of wave focusing.

An Experimental Method for Analysis of the Dynamic Behavior of Buoys in Extreme Environment (극한 환경하의 부표 운동성능 모형시험기법 개발)

  • Hong, Gi Yong;Yang, Chan Gyu;Choe, Hak Seon
    • Journal of Ocean Engineering and Technology
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    • v.15 no.3
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    • pp.134-141
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    • 2001
  • An experimental method to investigate the dynamic characteristics of buoys in extreme environmental condition is established. Because the buoy model requires a resonable size for accurate experiment, the test condition in model basin that satisfies the similarity law is hardly compatible with capability of test facilities. It is suggested that the linear wave component that is unable to satisfy similarity is separated with others. The model experiment is carried out with mitigated condition for the linear wave components while others including wave drift, current and wind are keeping the similarities. Then, the result can be extrapolated to give the dynamic behavior of buoys n extreme condition because linear wave component is solely responsibly to oscillatory buoy motion and other environmental components are applied as a initial tension. The similarity for current and wind conditions is viewed as equivalence of restoring forces. The validity of proposed method is examined with different types of standard ocean buoys and it indicates that the linearity of measured characteristics is assured with a limitation of resonable distance between test and estimated wave conditions.

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Experimental Analysis Method of the Dynamic Behavior of Buoys in Extreme Environment (극한 환경하의 부표 운동성능 모형시험기법 개발)

  • 홍기용;양찬규;최학선
    • Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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    • 2001.05a
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    • pp.208-215
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    • 2001
  • An experimental method to investigate the dynamic charasteristics of buoys in extreme environmental condition is established. Because the buoy model requires a resonable size for accurate experiment, the test condition in model basin that satisfies the similarity law is hardly met with capability of test facilities. It is suggested that the linear wave component that is unable to satisy similarity is separated with others. The model experiment can be carried out with mitigated condition for the linear wave components while others including wave drift, current and wind are keeping the similarities. Then the result is extrapolated to give the dynamic behavior of buoys in extreme condition because linear wave component is soley responsible to oscillatory buoy motion and other environmental components are applied as a initial tension. the similarity for current and wind conditions is viewed as equivalence of restoring forces. the validity of proposed method is examined with different types of standard ocean buoys and it indicates that the linearity of measured characteristics is assured with a limitation of resonable distance between test and estimated wave conditions.

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Extreme Climate Analysis and Adaptation Research on the Response of Climate Change in the Inland Region of the Korean Peninsula - Case of Deagu Metropolitan Area - (한반도 내륙 지역의 기후 변화 대응을 위한 극한기후 분석 및 적응 방안 연구 - 대구 광역시 사례를 중심으로 -)

  • Yamada, Keiko;Kim, Hae-Dong;Kim, Eun-Ji;Lee, Soon-Hwan
    • Journal of Environmental Science International
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    • v.29 no.7
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    • pp.773-784
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    • 2020
  • In order to protect the lives and property of citizens, the central and local governments are responding by enacting municipal ordinances and regulations as the frequency of extreme weather conditions due to climate change increases and intensity increases gradually. Accordingly, the basic contents and strategies of domestic and foreign policies to cope with cold and heat waves were reviewed, referring to measures suitable for application to the Daegu metropolitan area. In addition, it is intended to provide a policy alternative to Daegu metropolitan area to minimize damage from extreme weather by identifying the current status, characteristics, and future prospects of extreme weather in Daegu metropolitan area. Since the damage caused by the cold wave in Daegu area is not as great as that of other regions, it is urgent to come up with cold wave measures for the health and transportation sectors, and to come up with measures against the heat wave as the damage caused by the heat wave is the most serious in the country. Also we will identify spatial characteristics so that the districts and counties with high vulnerability to extreme weather can be identified and implemented first, and present civic life-oriented facilities and civic action guidelines to overcome cold and heat waves.

Numerical and experimental analysis of a wave energy converter in extreme waves

  • Ignacio P. Johannesen;Jose M. Ahumada;Gonzalo Tampier;Laura Gruter;Cristian Cifuentes
    • Ocean Systems Engineering
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    • v.13 no.3
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    • pp.225-245
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    • 2023
  • In the present paper, a numerical and experimental analysis for a wave energy converter under extreme environmental conditions is carried out. After the definition of design waves, including a 100-year return period stochastic sea state and a deterministic rogue wave condition, a numerical analysis using potential theory and a RANS equations solver are compared with experiments carried out at the Seakeeping Basin at the Technical University of Berlin. Results are discussed with special emphasis on the limits of potential theory methods for the evaluation of extreme wave conditions and the use of the presented methodology for early design stages.

The Effect of Sampling Rate on Statistical Properties of Extreme Wave (파랑자료의 sampling rate가 극한파의 통계에 미치는 영향)

  • Kim, Do Young
    • Journal of the Korean Society for Marine Environment & Energy
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    • v.16 no.1
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    • pp.36-41
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    • 2013
  • In this paper time series wave data are simulated using wave spectrum with random phases of the wave signal. The simulated wave signals are used to study the effect of the sampling rate on the ocean wave characteristics. Effect of sampling rate on wave data which include extreme wave such as freak waves are examined and various wave characteristics including abnormality index (AI), kurtosis of wave profile and maximum wave height are examined. Various wave heights are decreased as the sampling rate decreases. The zero-th moment of the wave spectrum does not affect much on the sampling rate but the second moment are greately affected on the sampling rate. The error due to the sampling rate is decreases as the wave period increases. The error in significant wave height based on the wave spectrum $H_s$ is smaller than that on the time domain method $H_{1/3}$. AI index and kurtosis of wave profile do not deviate much from the exact date as long as the sampling rate is greater than 1 Hz. Ocean wave measurement with the sampling frequency higher than 1 Hz will result the error less than 5% in estimating the height of extreme waves.

Reproduction of Extreme Waves Caused by Typhoon MAEMI with Wave Hindcasting Method, WAM (II) - Characteristics of extreme waves generated by Typhoon MAEMI in the south coast of Korea - (제3세대 파랑추산모형을 이용한 태풍 '매미'의 극한파랑 재현 (II) - 태풍 '매미'가 야기한 우리나라 남해안 일대의 극한파랑 특성 -)

  • Shin Seung-Ho;Hong Keyyong
    • Proceedings of the Korean Institute of Navigation and Port Research Conference
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    • 2004.11a
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    • pp.219-225
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    • 2004
  • Following a preceding study if Shin et al.(2004), wave fields for a month if September if 2003 are simulated based on the modified WAM cycle 4 model that enables the precise wave hindcasting with fine spatial meshes, and characteristics of extreme waves at the south roast if Koreo are analyzed The accuracy if applied wave model is verified by comparing computed wave parameters and corresponding ones measured at Ieodo ocean research station. The wave hindasting if typhoon 'Maemi' with an hour time interval reveals the extreme wave characteristics at 4 primary locations if south coast of Korea as follows: 1) At the front sea of Chaguido in the south of Jeju-do, the maximum significant wave height, moon wave period and mean wave direction appear to be 7.41m, 13.65s and $6.4^{\circ}$, respectively at 16:00 KST if Sep. 12, 2003. 2) At the entrance of Masan Bay, 12.50m, 13.65s and $1.2^{\circ}$ at 21:00 KST if Sep. 12. 3) At the front sea of Suyoung Bay, 13.85m, 13.81s and $0.2^{\circ}$ at 22;00 KST if Sep. 12. 4) At the front sea of Ulsan port, 11.00m, 13.25s and $28^{\circ}$ at 23:00 KST if Sep.

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Reproduction of Extreme Waves Caused by Typhoon MAEMI with Wave Hindcasting Method, WAM (II) - Characteristics of extreme waves generated by Typhoon MAEMI in the south coast of Korea - (제3세대 파랑추산모형을 이용한 태풍 ‘매미’의 극한파랑 재현 (II) - 태풍 ‘매미’가 야기한 우리나라 남해안 일대의 극한파랑 특성 -)

  • Shin, Seung-Ho;Hong, Key-Yong
    • Journal of Navigation and Port Research
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    • v.28 no.8
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    • pp.745-751
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    • 2004
  • Following a preceding study of Shin et al.(2004), wave fields for a month of September of 2003 are simulated based on the modified WAM cycle 4 model that enables the precise wave hindcasting with fine spatial meshes, and characteristics of extreme waves at the south coast of Korea are analyzed The accuracy of applied wave model is verified by comparing computed wave parameters and corresponding ones measured at Ieodo ocean research station. The wave hindcasting of typhoon 'Maemi' with an hour time interval reveals the extreme wave characteristics at 4 primary locations of south coast of Korea as follows: 1) At the front sea of Chaguido in the south of Jeju-do, the maximum significant wave height, mean wave period and mean wave direction appear to be 7.41m, 13.65s and $6.4^{\circ}$ respectively at 16:00 KST of Sep. 12, 2003. 2) At the entrance of Masan Bay, 12.50m, 13.65s and $1.2^{\circ}$ at 21:00 KST of Sep. 12. 3) At the front sea of Suyoung Bay, 13.85m, 13.81s and $0.2^{\circ}$ at 22;00 KST of Sep. 12. 4) At the front sea of Ulsan port, l1.00m, 13.25s and $2.8^{\circ}$ at 23:00 KST of Sep. 12.