6 releases
0.2.1 | Jul 8, 2024 |
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0.2.0 | Jul 8, 2024 |
0.1.3 | Jul 6, 2024 |
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JONSWAP
Lib and CLI to calculate JONSWAP wave spectrum and its realisation in time domain.
Use:
jonswap hs tp [-n nharms] [-g gamma] [-s seed] [-d duration] [-t timestep] [-p{s|t}] [-h]
where:
hs : significant wave height in meters.
tp : spectral peak period in seconds
-n : number of harmonics used to discretise the spectrum. Default 200.
-g : value for gamma. Default as per DNV.
-s : seed number for phase randomisation.
-d : duration - timetrace will be shown. Default 120s.
-t : time step. Default is 0.1 seconds.
-p{s|t} : gnuplot friendly output of spectrum (-ps) or timetrace (-pt),
to be piped to `gnuplot -p -e "plot '-' using i:j w l"` where
`i:j` are the index of the columns to be used as x and y axis.
Note this only works for 1 plot. For multiple plots, need to
save the output to a temporary file.
-h : show this help.
Example
Spectrum and a time realisation of a Hs 2.5m, Tp 7s, using default parameters, ie, 200 harmonics and gamma calculated as per DNV.
$ jonswap 2.5 7
Wave Hs : 2.50 m
Wave Tp : 7.00 s
Wave Gamma : 1.932 -
Spectral moment m0 : 0.3897 m²
Spectral moment m2 : 0.5635 m²(rd/s)²
Spectral moment m4 : 2.5620 m²(rd/s)^4
Hm0 : 2.4970 m
Spectrum
========
T w PM JS amp phi
[s] [rd/s] [m²s/rd] [m²s/rd] [m] [rd]
20.000 0.314159 0.00000000 0.00000000 0.00000 1.61987
19.633 0.320037 0.00000000 0.00000000 0.00000 -0.30448
...
0.500 12.566371 0.00000405 0.00000328 0.00000 -1.51897
Time History
============
Time Elevation
0.000 0.697963
0.100 0.734472
0.200 0.748701
...
119.900 -1.200554
120.000 -1.180046
Simple plot
The spectrum can be plotted to terminal using GNUPLOT:
$jonswap 2.5 7 -ps | gnuplot -p -e "set terminal dumb; plot '-' using 1:4 w l"
1 +--------------------------------------------------------------------+
| + + + * + + + + + + |
0.9 |-+ * * '-' using 1:4 *******-|
| * * |
0.8 |-+ * * +-|
| * * |
0.7 |-+ * * +-|
| * * |
0.6 |-+ * * +-|
| * * |
0.5 |-+ * * +-|
| ** * |
0.4 |-+ * * +-|
| ** * |
0.3 |-+ ** * +-|
| ** ** |
0.2 |-+ ** * +-|
| ** * |
0.1 |-+ *** * +-|
| + ****+ + + *** + + + + |
0 +--------------------------------------------------------------------+
0 2 4 6 8 10 12 14 16 18 20
By removing the line set terminal dumb;
you can get proper plots. Or, if you
want more control over the plot, there's a convenience Python script plt.py
which generates images like these:
Dependencies
~315KB