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Calibration Parameters
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Figure 5.36 Example of a sponge layer map
1DH Boussinesq wave module
In connection with modelling of non-linear wave transformation on coastal
profiles sponge layers are usually applied at the two model domain extremes.
As for 2D applications the sponge layers at j= 0 are used for absorption of
wave energy propagation out of the model domain. The purpose of having
sponge layers at the other extreme (i.e. at j= jextr) is to either absorb incom-
ing waves in areas where no computation is requested (see left-hand side fig-
ure below) or to reduce oscillations in the slot (applied in connection with
Moving shoreline, see right-hand figure below).
Figure 5.37 Example of sponge layer profiles. The panel to the left shows a profile
without moving shoreline and the right panel shows profile including
moving shoreline.
Specifying sponge layer
You can choose not to include sponge layers, or to specify the sponge layers
by providing your model setup with a map/profile including sponge layer coef-
ficients, in much the same way as you specify porosity values. The map/pro-
file is read from a data file (dfs2 or dfs1).
General guidelines for the preparation of this map/profile are as follows:

very good absorbing characteristics are obtained for a sponge layer
width of one to two times the wave length corresponding to the most
energetic waves

for typical short-wave studies (grid spacings of 3-10 m) the sponge lay-
ers should be at least 20 lines wide