MIKE 21 BW, User Manual, Page: 41 / 196

2DH Boussinesq Wave Module - Examples
41
Figure 4.15 Torsminde Harbour, Denmark. The red dot in the lower panel shows the
location
In this example the occurrence of the long-period waves is caused by interac-
tions of short-period wind waves. The shoaling and breaking of the short-
period wave trains are non-linear processes involving a number of compli-
cated details. Quadratic interactions between harmonics in shallow water
lead to substantial cross-spectral energy transfer over relatively short dis-
tances, and during shoaling still more energy will be transferred into bound
sub-harmonics and super-harmonics. In a number of situations, part of the
energy may be released as free harmonics, e.g. during passage over sub-
merged bars or reefs, during diffraction around a breakwater, or during the
process of breaking. When wave breaking occurs, the primary waves will
start dissipating, and this will allow for a gradual release of the bound sub-
harmonics and result in free long waves moving towards the shoreline and
harbour entrance.