
Reference Manual
176
MIKE 21 BW - © DHI
If the blow-up occurs near the moving shoreline (and a low pass filter is used)
please increase the slot width and/or slot depth, see also Section 5.3.9 Mov-
ing shoreline.
1DH simulations with wave breaking and moving shoreline
When a blow-up occurs in a 1DH application it happens most often near the
swash zone. The first step is to reduce the time step and next to increase the
slot width.
If a blow-up occurs outside the surf/swash zone please set the so-called sup-
g_coefficient to e.g. 0.1 in an OPTION section (see Section 5.5.15). The
default value is 0.05. It is not recommended to use a SUPG coefficient larger
than 0.25.
Blow-up using the enhanced equations
Even though the minimum wave period is resolved by approximately 35 time
steps, instabilities may appear. An example is shown below in Figure 5.54.
Then the time step should be reduced to a temporal resolution of 50 points
per wave period. If instabilities still appear, then you may try using a partly lin-
ear time-extrapolation of the cross-Boussinesq terms. Excluding the extrapo-
lation will result in some artificial damping of waves propagating with an angle
to the grid, and the effect will the enhanced for increasing water depth to
deep water wave length. However, partly time-extrapolation applied in a local
area will usually not affect the overall results. More information at partly time-
extrapolation.
Please note: Exclusion of the time extrapolation (i.e. time extrapolation factor
= 0) should only be used as a last resort.
Figure 5.54
Example of blow-up near an internal generation line
Boundary/generation wave data
In order to avoid an instability you may consider generating new open bound-
ary or internal generation data using a different initial random seed. The over-
all statistics of the data will not change (it is just a different realisation).
Содержание 21 BW
Страница 1: ...MIKE 2017 MIKE 21 BW Boussinesq Waves Module User Guide...
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Страница 4: ...4 MIKE 21 BW DHI...
Страница 13: ...General Description 13 Figure 2 4 Simulation of wave penetration into Frederikshavn harbour Denmark...
Страница 16: ...Introduction 16 MIKE 21 BW DHI...
Страница 75: ...2DH Boussinesq Wave Module Examples 75 Figure 4 45 Visualisation 2D of instantaneous surface elevation...
Страница 185: ...Entries Arranged Alphabetically 185 Figure 5 58 Application of different time extrapolation factors...
Страница 190: ...Reference Manual 190 MIKE 21 BW DHI...
Страница 192: ...Scientific Documentation 192 MIKE 21 BW DHI...
Страница 193: ...193 INDEX...