Dfsu - spectral data¶
MIKE 21 SW can output full spectral information in points, along lines or in an area. In all these cases data are stored in dfsu files with additional axes: frequency and directions.
This notebook explores reading full spectral dfsu files from MIKE 21 SW as
- point
- line
- area
In [1]:
import numpy as np
import matplotlib.pyplot as plt
import mikeio
Read dfsu point spectrum¶
In [2]:
fn = "../tests/testdata/spectra/pt_spectra.dfsu"
da = mikeio.read(fn)[0]
da
Out[2]:
<mikeio.DataArray> name: Point 1: Energy density dims: (time:31, direction:16, frequency:25) time: 2017-10-27 00:00:00 - 2017-10-27 05:00:00 (31 records) geometry: Point Spectrum Geometry(frequency:25, direction:16)
In [3]:
da.plot(); # plots first timestep by default
Don't like the default plot? No worries, it can be customized.
In [4]:
ax = da.plot.patch(rmax=8)
dird = np.round(da.directions, 2)
ax.set_thetagrids(dird, labels=dird);
Dfsu line spectrum¶
Data in dfsu line spectra is node-based contrary to must other dfsu-formats.
In [5]:
fn = "../tests/testdata/spectra/line_spectra.dfsu"
da = mikeio.read(fn).Energy_density
da
Out[5]:
<mikeio.DataArray> name: Energy density dims: (time:4, node:10, direction:16, frequency:25) time: 2017-10-27 00:00:00 - 2017-10-27 05:00:00 (4 records) geometry: DfsuSpectral1D (9 elements, 10 nodes)
In [6]:
spec = da[0].isel(node=3) # note first 3 points are outside domain
spec
Out[6]:
<mikeio.DataArray> name: Energy density dims: (direction:16, frequency:25) time: 2017-10-27 00:00:00 (time-invariant) geometry: Point Spectrum Geometry(frequency:25, direction:16, x:1.89843, y:51.69084)
In [7]:
spec.plot(cmap="Greys", rmax=8, r_as_periods=True);
Plot Hm0 on a line¶
In [8]:
Hm0 = da.isel(time=0).to_Hm0()
Hm0.plot(title='Hm0 on a line crossing the domain');
Dfsu area spectrum¶
In [9]:
fn = "../tests/testdata/spectra/area_spectra.dfsu"
da = mikeio.read(fn, items="Energy density")[0]
da
Out[9]:
<mikeio.DataArray> name: Energy density dims: (time:3, element:40, direction:16, frequency:25) time: 2017-10-27 00:00:00 - 2017-10-27 05:00:00 (3 records) geometry: DfsuSpectral2D (40 elements, 33 nodes)
In [10]:
da.plot(); # default area plot is Hm0
In [11]:
da_pt = da.sel(x=2.9, y=52.5)
da_pt
Out[11]:
<mikeio.DataArray> name: Energy density dims: (time:3, direction:16, frequency:25) time: 2017-10-27 00:00:00 - 2017-10-27 05:00:00 (3 records) geometry: Point Spectrum Geometry(frequency:25, direction:16, x:2.90053, y:52.47039)
In [12]:
da_pt.plot(rmax=9);
Interactive widget for exploring spectra in different points¶
In [13]:
from ipywidgets import interact
from datetime import timedelta
In [14]:
@interact
def plot_element(id=(0,da.geometry.n_elements-1), step=(0,da.n_timesteps-1)):
spec = da[step,id]
time = da.start_time + timedelta(seconds=(step*da.timestep))
spec.plot(vmax=0.04, vmin=0, rmax=8, title=f"Wave spectrum, {time}, element: {id}")
plt.show()
interactive(children=(IntSlider(value=19, description='id', max=39), IntSlider(value=1, description='step', ma…
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