MIKE 21 BW, User Manual, Page: 113 / 196

Basic Parameters
113
Figure 5.5 Enclosed harbour with reduced computational area
In the example, the shallow area inside the harbour is also converted to arti-
ficial land values, for two reasons:

It is assumed that the shallow area/beach will absorb the wave energy.
Therefore sponge layers will be placed in front of the land values.

The minimum water depth in the model area defines the grid spacing, as
the minimum wave length is defined by the minimum water depth in com-
bination with the minimum wave period (see Selecting the grid spacing
below). Therefore very shallow areas should be avoided (if wave break-
ing is not included), where possible, to reduce the CPU demand.
The areas, unimportant for the propagation into the harbour, may differ for dif-
ferent incoming wave directions. This is described in Setup of internal gener-
ation lines, section 5.3.4.
In other applications, such as semi-enclosed harbours, along exposed coast-
lines, or around offshore structures, the area to be modelled is not as well
defined. Then, it is important that the model is extended far enough from the
area of interest to ensure that model results will not be influenced by close
proximity to the model boundaries.
As a rule-of-thumb, the minimum distance between the end of a structure and
an adjacent closed boundary should preferably be five or six characteristic
wave lengths.
Selecting a coastal profile (1DH)
In deciding the coastal profile to be included in your model, you must consider
the profile of interest, and the positions and types of the model boundaries to
be used. You also have to consider whether wave breaking and moving
shoreline should be included.