7.6. IRREGULAR (2-D) WAVE GENERATION
407
5. Synthesize a new wave board time series realization and
generate the new wave condition in the wave facility.
6. Continue this iterative process until a satisfactory laboratory wave train is achieved. Goda (1985) recommended
that several test realizations be made, and the tests should
be long enough to give stable wave statistics.
This iterative correction method is better suited for irregular waves synthesized by the DSA method because less spectral variation occurs between
time series realizations determined by the DSA method.
The correction method can also be used to “calibrate” laboratory waves
that undergo shoaling, refraction, diffraction, and/or other transformations
between the wave board and position where we wish to simulate the target
spectrum. This is a particularly useful technique for laboratory basins that
include complex bathymetry or other features that may impact the accuracy
of irregular wave transformations calculated with numerical models.
Daemrich, Eggert, Kohlhase (1980) and Daemrich and Eggert (1981)
reported success using the iterative approach for generating irregular wave
trains fitting the target spectrum. However, they noted that this linear
method fails, as expected, when wave breaking occurs between the wave
board and the point of wave measurement.
Generation of Measured Irregular Waves
It has been argued that laboratory reproduction of actual wave trains measured in the prototype are preferable in some instances to synthesized laboratory wave trains. Examples where measured wave records may be useful
include projects such as tests of rubble-mounds structure stability, measurement of shock forces, and studies of floating structure response to irregular
waves. In these cases naturally occurring wave groups might be considered
important.
On the other hand, critics argue that the method is limited because of
the large number of possible conditions that would have to be acquired and
stored. The method also implies that the field measured data have captured the correct field condition needed for testing. Perhaps it is better to
synthesize a large number of irregular wave trains, then select and generate
those segments that appear to meet the parameters thought to be critical
for the project being tested. In either case, we are confronted with the
problem of determining the necessary irregular wave board displacement
time series that will result in the desired sea surface elevation wave time
series in the wave facility.
If there is no requirement to reproduce specific portions of the irregular
wave time series at a specific location in the wave facility, measured wave
407
5. Synthesize a new wave board time series realization and
generate the new wave condition in the wave facility.
6. Continue this iterative process until a satisfactory laboratory wave train is achieved. Goda (1985) recommended
that several test realizations be made, and the tests should
be long enough to give stable wave statistics.
This iterative correction method is better suited for irregular waves synthesized by the DSA method because less spectral variation occurs between
time series realizations determined by the DSA method.
The correction method can also be used to “calibrate” laboratory waves
that undergo shoaling, refraction, diffraction, and/or other transformations
between the wave board and position where we wish to simulate the target
spectrum. This is a particularly useful technique for laboratory basins that
include complex bathymetry or other features that may impact the accuracy
of irregular wave transformations calculated with numerical models.
Daemrich, Eggert, Kohlhase (1980) and Daemrich and Eggert (1981)
reported success using the iterative approach for generating irregular wave
trains fitting the target spectrum. However, they noted that this linear
method fails, as expected, when wave breaking occurs between the wave
board and the point of wave measurement.
Generation of Measured Irregular Waves
It has been argued that laboratory reproduction of actual wave trains measured in the prototype are preferable in some instances to synthesized laboratory wave trains. Examples where measured wave records may be useful
include projects such as tests of rubble-mounds structure stability, measurement of shock forces, and studies of floating structure response to irregular
waves. In these cases naturally occurring wave groups might be considered
important.
On the other hand, critics argue that the method is limited because of
the large number of possible conditions that would have to be acquired and
stored. The method also implies that the field measured data have captured the correct field condition needed for testing. Perhaps it is better to
synthesize a large number of irregular wave trains, then select and generate
those segments that appear to meet the parameters thought to be critical
for the project being tested. In either case, we are confronted with the
problem of determining the necessary irregular wave board displacement
time series that will result in the desired sea surface elevation wave time
series in the wave facility.
If there is no requirement to reproduce specific portions of the irregular
wave time series at a specific location in the wave facility, measured wave