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5.5.4
Blow-up
MIKE 21 BW checks the requests and input from you as much as possible,
but in order to minimise the number of restrictions on potential applications, it
is allowed to request MIKE 21 BW to perform unrealistic simulations. Also,
MIKE 21 BW is an advanced numerical model, which means that the possibil-
ity of numerical instabilities (“blow-ups”) exists. Finally, no software product,
including MIKE 21 BW, is completely error free.
The sections below describe what to do if errors occur during the first few
time steps, or after some time steps have been completed. Also help in case
of model crash before the first time step is given.
Blow-up after the first few time steps
General description
You have started the execution of a simulation and it stops after the message
(in the .log-file “Time step: 1”, and possibly “Time step: 2”, and a few more
time steps have been written.
Normally this type of error is caused by an inconsistency in the simulation
setup. Therefore, please check your model specifications carefully.
Near the end of the .log file you get the message:
“-----BLOW-UP detected-----”
In other words, you have encountered a numerical instability. However, as it
occurs very early in the simulation it is most likely caused by an inexpedient
combination of model input.
What to do?
If one or more time steps have been completed you should make a contour
plot of surface elevation of the last one of these time steps. These plots will
probably show you in which part of the domain the blow-up occurs. Notice,
that first you may need to re-run the simulation storing the results at every
time step and in every grid point.
Using the plots as a guideline you should check the following:
1.
That the bathymetry has been specified correctly, and that the grid spac-
ing is sufficiently small to adequately resolve the waves specified in the
open boundary conditions, or at the internal generation line
2.
That the time step is sufficiently small to adequately resolve the waves
and surface rollers
3.
That the Courant number is less than one (0.5 in the 1DH module)
Содержание 21 BW
Страница 1: ...MIKE 2017 MIKE 21 BW Boussinesq Waves Module User Guide...
Страница 2: ...2...
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...