scientimate.seaswell1d

fseparation, Hm0, Hm0sea, Hm0swell, Tp, Tpsea, Tpswell, m0, m0sea, m0swell, fp, Tm01, Tm02 = scientimate.seaswell1d(f, Syy, fsepCalcMethod='hwang', fu=0.5, fmaxswell=0.2, fpminswell=0, Windvel=10, dispout='no')

Description

Partition (separate) wind sea from swell in a power spectral density using an one dimensional method

Inputs

f

Frequency (Hz)

Syy

Power spectral density (m^2/Hz)

fsepCalcMethod=’hwang’

Wind sea swell separating calculation method

‘celerity’: using deep water wave celerity, ‘gilhousen’: Gilhousen and Hervey (2001),

‘hwang’: Hwang et al. (2012), ‘exact’: calculate exact value

fu=0.5

An upper bound of a spectrum integration frequency (Hz)

fmaxswell=0.25

Maximum frequency that swell can have, It is about 0.2 in Gulf of Mexico

fpminswell=0.1

A lower bound of a spectrum (minimum frequency) that is used for Tpswell calculation

Windvel=10

Wind velocity (m/s), only required for Gilhousen and Hervey (2001) method

dispout=’no’

Define to display outputs or not (‘yes’: display, ‘no’: not display)

Outputs

fseparation

Wind sea and Swell Separation Frequency (Hz)

Hm0

Zero-Moment Wave Height (m)

Hm0sea

Sea Zero-Moment Wave Height (m)

Hm0swell

Swell Zero-Moment Wave Height (m)

Tp

Peak wave period (second)

Tpsea

Peak Sea period (second)

Tpswell

Peak Swell Period (second)

m0

Zero-Moment of the power spectral density (m^2)

m0sea

Zero-Moment of the wind sea spectrum (m^2)

m0swell

Zero-Moment of the swell spectrum (m^2)

fp

Peak wave frequency (Hz)

Tm01

Wave Period from m01 (second), Mean Wave Period

Tm02

Wave Period from m02 (second), Mean Zero Crossing Period

Examples

import scientimate as sm
import numpy as np

N=2**11 #Total number of points
fs=2 #Sampling frequency
df=fs/N #Frequency difference
f=np.arange(0,fs/2+df,df) #Frequency vector
f[0]=f[1]/2 #Assign temporarily non-zero value to fisrt element of f to prevent division by zero
SyySea=0.016*9.81**2/((2*np.pi)**4*(f**5))*np.exp(-1.25*(0.33/f)**4) #Calculating Spectrum
SyySwell=0.016*9.81**2/((2*np.pi)**4*(f**5))*np.exp(-1.25*(0.15/f)**4)*0.005 #Calculating Spectrum
Syy=SyySea+SyySwell
f[0]=0
Syy[0]=0
fseparation,Hm0,Hm0sea,Hm0swell,Tp,Tpsea,Tpswell,m0,m0sea,m0swell,fp,Tm01,Tm02=sm.seaswell1d(f,Syy,'exact',0.5,0.3,0,10,'yes')

References

Gilhousen, D. B., & Hervey, R. (2002). Improved estimates of swell from moored buoys. In Ocean Wave Measurement and Analysis (2001) (pp. 387-393).

Hwang, P. A., Ocampo-Torres, F. J., & García-Nava, H. (2012). Wind sea and swell separation of 1D wave spectrum by a spectrum integration method. Journal of Atmospheric and Oceanic Technology, 29(1), 116-128.