NRCEST 國立交通大學土木工程學系 中華民國 102 年 3 月 28 日

Reference 2

methods 3

Significant wave representation 4 Individual wave H 1 >H 2 >H 3 … Brestchneider (1968) H 1/3 : 前 1/3 大之個別波波高平均值 (significant wave, 示性波 ) T 1/3 : 相對於大小排序波高之週期平均值 Neir et al. (2003) T 1/3 :T 1 >T 2 >T 3 … 週期仿照示性波高前 1/3 大之平均值週期

Statistical properties 5 Rayleigh distribution

Representative wave height 6

7

Statistical theory for irregular waves 8

Rayleigh distribution for wave height 9

10

Rayleigh distribution for wave height 11

Rayleigh distribution for wave height 12

1/Nth Waves for Rayleigh distribution 13

1/Nth Waves for Rayleigh distribution 14

1/Nth Waves for Rayleigh distribution 15

1/Nth Waves for other distributions 16

Regular wave 17

Irregular wave 18

Frequency spectrum of irregular waves 19 Fourier transform (Fast FT)

Frequency spectrum of irregular waves 20 Brestchneider (1968) Goda (1988) Wallops spectrum by Hwung et al. (1981)

Frequency spectra of irregular waves 21 JONSWAP (1973)

Directional Spectrum of sea waves 22 G(θ) : directional distribution of energy spectrum S(f) : energy (power) spectrum

Directional Spectra of sea waves 23 Mitsuyasu (1975) Smax: Spreading parameter

Directional Spectra of sea waves 24 Smax=20

Relationship between spectra and wave height 25 Zeroth moment of spectrum

Relationship between spectra and wave height 26

Relationship between spectra and wave period 27 Zeroth and second moments of spectrum

Spectra of sea waves-Example I 28

Example I 29 Directional spectrum

Example-I 30 sample average of sixteen directional spectra directional spectra of in-site buoy measurements

Example-I 31 directional spreading function Power spectrum

Example-II 32

Example-II 33

Example-II 34