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Output Parameters
167
Figure 5.50 Definition of start-up period
The “start-up period” can be estimated using simple linear wave theory. Cal-
culate the wave group velocity and estimate how long the travel time is for the
first wave (e.g. the wave with the spectral peak period, T
p
) to propagate from
the boundary/wave generation line to the innermost part of the harbour. Add
to this time e.g. 30 peak wave periods. The total time can be considered as
an estimation of the “start-up period”. The total duration of the simulation is
the “start-up period”, plus not less than 15 - 20 min. (which is usually the min-
imum). The calculation of the wave disturbance coefficients should be started
at arrival of e.g. wave No. 30, and the calculation period should normally
cover the time step range specified on the Simulation Period dialog.
The “start-up period” should not be confused with the warm-up period.
Regular waves
For regular waves the wave disturbance coefficients can be calculated for a
period covering only a few wave periods after a quasi-steady state is
reached. In this case the first wave to use in the calculation should be set to
zero. Then the calculation will be performed from the first time step of the
selected period. Note that for regular waves the significant wave height is a
factor
larger than the wave height.
5.4.4 Moving shoreline parameters
The moving shoreline output MIKE 21 BW 1DH application only consists of
time series containing the following three output items:

Horizontal run-up

Vertical run-up

Total run-up
2