WaveSpectrum

The WaveSpectrum class provides an interface for handling 2-D directional wave spectra. WaveSpectrum extends DirectionalSpectrum, and contains spectrum density values on a two-dimensional frequency/(wave)direction grid.

\[S_{\zeta}(\omega, \theta)\]

The WaveSpectrum is initialized with a frequency list (1-D array), a direction list (1-D array) and corresponding wave spectrum density values (2-D array).

import numpy as np
import waveresponse as wr


freq = np.linspace(0.0, 1.0, 50)
dirs = np.linspace(0.0, 360.0, endpoint=False)
vals = np.random.random((len(freq), len(dirs)))

wave = wr.WaveSpectrum(
    freq,
    dirs,
    vals,
    freq_hz=True,
    degrees=True,
    clockwise=False,
    waves_coming_from=False,
)

Alternatively, you can construct a WaveSpectrum from a ‘non-directional’ spectrum (1-D array), a directional spreading function and a peak direction:

import numpy as np
import waveresponse as wr


freq = np.linspace(0.0, 1.0, 50)
dirs = np.linspace(0.0, 360.0, endpoint=False)
spectrum1d = np.random.random(len(freq))
dirp = 45.0

def spread_fun(f, d):
    return (1.0 / 180.0) * np.cos(np.radians(d / 2)) ** 2

wave = wr.WaveSpectrum.from_spectrum1d(
    freq,
    dirs,
    spectrum1d,
    spread_fun,
    dirp,
    freq_hz=True,
    degrees=True,
    clockwise=False,
    waves_coming_from=False,
)

Tip

Two standardized (cosine-based) spreading functions, CosineFullSpreading and CosineHalfSpreading, are provided by waveresponse.

The WaveSpectrum class extends the DirectionalSpectrum class with the following:

Calculate the significant wave height, Hs:

wave.hs

Calculate the wave peak period, Tp:

wave.tp

Calculate the wave peak direction:

wave.dirp()

Calculate the mean wave direction:

wave.dirm()