MIKE 21 BW, User Manual, Page: 27 / 196

2DH Boussinesq Wave Module - Examples
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problem can be solved using the classical Boussinesq equations (i.e. the dis-
persion coefficient is B= 0).
The grid spacing is selected to be 5 m and the time step is 0.5 s. The simula-
tion duration is 10 minutes (1201 time steps).
Although a 10 point thick sponge layer is used in this example you are in gen-
eral recommended to apply at least 20 point wide sponge layers in most prac-
tical applications of the 2DH Boussinesq Wave Module. Excellent wave
absorbing characteristics have been obtained for sponge layers having a
thickness of 1-2 times the wave length of the most energetic waves (corre-
sponding to the spectral peak wave period). In this example the thickness of
the 10 point wide sponge layer is 0.5-0.6 times the wave length correspond-
ing to the spectral peak wave period. However, from the results shown in
Figure 4.2 (panel showing the significant wave height) it is hard to detect any
spurious reflections from the sponge layers.
Model results
A time series of the simulated surface elevation extracted at point P(35,5) is
shown in Figure 4.2, as well as the spatial variation of the significant wave
height along the channel. Note that the significant wave height is less than 1
m as the incident wave spectrum is not re-scaled.
Figure 4.2 Model results. Time series of simulated surface elevation at a given
point (upper panel) and line series of the stationary significant wave
height along the centre line (lower panel)