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NRCEST
Wave statics
Chang Hsien Kuo
國立交通大學土木工程學系中華民國 102年 3月 28日
2
Reference
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methods
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Significant wave representation
Individual wave H1>H2>H3… Brestchneider (1968)
H1/3: 前 1/3 大之個別波波高平均值 (significant wave, 示性波 )T1/3: 相對於大小排序波高之週期平均值Neir et al. (2003)T1/3:T1>T2>T3… 週期仿照示性波高前 1/3 大之平均值週期
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Statistical properties
Rayleigh distribution
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Representative wave height
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Representative wave height
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Statistical theory for irregular waves
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Rayleigh distribution for wave height
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Rayleigh distribution for wave height
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Rayleigh distribution for wave height
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Rayleigh distribution for wave height
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1/Nth Waves for Rayleigh distribution
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1/Nth Waves for Rayleigh distribution
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1/Nth Waves for Rayleigh distribution
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1/Nth Waves for other distributions
表 2.3-1 計算 Weibull 及 Gauss 分布示性波之理論統計公式
分布函數 計算示性波公式
Weibull 分布 )3ln,1
(3
])3[(ln1
Normal 分布
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3
2
32
2 p
xx
Erfcep
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Regular wave
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Irregular wave
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Frequency spectrum of irregular waves
Fourier transform (Fast FT)
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Frequency spectrum of irregular waves
Brestchneider (1968)
Goda (1988)
Wallops spectrum by Hwung et al . (1981)
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Frequency spectra of irregular waves
JONSWAP (1973)
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Directional Spectrum of sea waves
G(θ) : directional distribution of energy spectrum
S(f) : energy (power) spectrum
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Directional Spectra of sea waves
Mitsuyasu (1975)
Smax: Spreading parameter
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Directional Spectra of sea waves
Smax=20
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Relationship between spectra and wave height
Zeroth moment of spectrum
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Relationship between spectra and wave height
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Relationship between spectra and wave period
Zeroth and second moments of spectrum
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Spectra of sea waves-Example I
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Example I
Directional spectrum
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Example-I
sample average of sixteen directional spectra
directional spectra of in-site buoy measurements
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Example-I
directional spreading function
Power spectrum