MIKE 21 BW, User Manual, Page: 141 / 196

Calibration Parameters
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applications. In such situations we recommend you to introduce a slot friction
coefficient, e.g. 0.01-0.1. You may also increase the width and/or the depth of
the slot.
5.3.10 Porosity layers
Porosity values are used to model either partial reflection and/or transmission
through structures. If porosity values are backed up by land, partial reflection
will take place. Conversely, (partial) transmission will also take place if the
porosity values are not backed up by land points.
The porosity values at open water grid points should be set to unity (i.e.
porosity = 1.0).
The porosity should only be set to less than unity along structures where you
want to include the dissipation effect of porous flow.
2DH Boussinesq wave module
In the figure below is shown an example where a porosity layer is applied to
model partial reflection in case of a wave disturbance study.
Figure 5.28 Example of porosity map
The width of the porosity layer should normally be at least 1/4 of a wave
length (for 1 DH application too) corresponding to the most energetic waves.
In 2D applications this most often corresponds to a three to five grid points
wide layers.
The water depth in the porous layer should be almost uniform.