taken looking along the crest of the 30.5-m-long wave front created by the
synchronized generators.
For both of the above mentioned batch files, the last step in the synthesis
process is to convert the four individual drive signals (initially in GEDAP file
format) into a single file consisting of four arrays of data (MTS file format); one
array for each of the four wave machine drive signals. Therefore, the final output
from both of these batch files is a single file containing the synchronized drive
signals for all four wave generators.
Generating waves
Waves are generated using the wave machine drive signal file in the Wave
Programs control panel, found under the Operation menu of the MTS control
software. The layout of this control panel is shown in Figure 39. The operator
can select the length of time for which waves will be generated by selecting the
desired number of times the file should be repeated.
The operator should visually observe
and listen to the wave generators for the
full duration of the drive signal when a
new drive signal is initially used to
generate waves, especially irregular
waves. The operator should visually
check if the wave generators are properly
synchronized, as illustrated previously in
Figure 5. If they are not, one or more of
the parameters discussed above may be
defined incorrectly. Another common
problem is vibrations of the wave
generators (i.e., mechanical "clunking"),
which may be heard at high-frequency
wave periods. In some cases, these
vibrations can be very severe. This not
only decreases the quality of the wave
field but will also cause damage to the
wave generators if allowed to operate for
extended periods of time. This problem is
normally caused by generating waves with
a frequency too high relative to the
magnitude of the wave height. For the
case of irregular waves, the upper cutoff
frequency, an input parameter in the
Figure 39. Wave programs control panel in
the MTS control software
program RWREP5, should not exceed
(Permission to reprint granted by
approximately 1.5 to 2.0 Hz for the case of
MTS Systems Corp.)
irregular waves. Selection of the proper
upper cut-off frequency is normally
determined by trial and error.
67
Chapter 7
Wave Generation and Current Recirculation
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