be applied, whereas the latter experiment would be at the limit of application
for the model. However, because the C&K data encompassed several tests
with wave blocking, it provided an opportunity to investigate how well the
routine in NMLong-CW would predict this mechanism (and the efficiency of
the model in describing the situation). Also, because the C&K data were
representative of deep water, the model could be evaluated for such
conditions with emphasis on energy dissipation produced by breaking at
greater water depths (i.e., breaking due to limitations in the wave steepness)
and how to model this.
The enhanced version of NMLong-CW reproduced the CHL-I data well,
validating the generalized formulation of the Dally (1980) model for wave
breaking on a current. No modifications of the empirical coefficient values
were needed, with standard values employed. In the simulations of the C&K
data, the same standard values, NMLong-CW produced robust and acceptable
results for most of the tests, at least regarding the blocking location and
maximum wave height. A new, improved description of the stable wave
height after breaking would increase the agreement between calculations and
measurements, but it was considered outside the scope of the present study to
develop such a relationship. Also, as observed by Chawla and Kirby (1998,
2002), the current speed needed for blocking predicted by linear theory was
lower than what was measured. Thus, the model would be on the
conservative side regarding the prediction of blocking and the associated
maximum wave height.
In summary, NMLong-CW was found to be suitable for calculating wave
shoaling, breaking, and blocking on an opposing current at limited water
depths, producing robust and reliable results with no calibration. In
applications for deep water, the model still displayed robust behavior and
yielded acceptable results for blocking location and maximum wave height,
but larger uncertainties should be expected regarding details of the variation
in wave height after breaking.
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Chapter 4 Verification of Wave Model
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