Tuesday, 14 January 2020: 3:45 PM
158 (Boston Convention and Exhibition Center)
Recent publications and ongoing research have shown that a number of assumptions imbedded within
today’s wave models do not provide accurate wave spectra or wave heights necessary for coastal
storm planning and offshore activities. The fundamental problem will be shown here to be related to
a misrepresentation of the nonlinear source term. As shown in earlier publications by the presenter,
the form of this source term within the models such as WAM and Wavewatch III (the Discrete
Interaction Approximation, DIA) does not contain an adequate number of degrees of freedom
required to provide accurate representations of nonlinear energy and momentum transfers within the
spectrum. In turn, this creates a need for the wind and wave breaking source terms to play artificial
roles in reproducing much of the behavior observed in turning winds situations and to be calibrated
to include these artificial aspects into the total wave physics. Unfortunately, the wind and breaking
source terms also lack the dimensionality required to represent the physics of wave source terms in
these situations.
This presentation provides comparisons of results from detailed-balance simulations in which the
exact integral is used to represent the nonlinear source Results from these simulations show that the
DIA cannot reproduce key spectral behavior observed in the wave spectra around the world. The
presentation then proceeds to develop new physical bases for both the wind input and wave breaking
source terms. These new source terms are both recast in a fashion which considers the probabilistic
contributions of all waves within the spectrum on wind input and wave breaking.
The new breaking term and wind input terms are then generalized into forms applicable to arbitrary
depth. In this form, the new spectral balance produces an evolutionary spectral form that is, in some
aspects, similar to the TMA spectrum hypothesized in 1985 by Bouws et al.. Comparisons of spectra
produced by a model containing the new set of source terms are compared to observations, with very
encouraging results.
today’s wave models do not provide accurate wave spectra or wave heights necessary for coastal
storm planning and offshore activities. The fundamental problem will be shown here to be related to
a misrepresentation of the nonlinear source term. As shown in earlier publications by the presenter,
the form of this source term within the models such as WAM and Wavewatch III (the Discrete
Interaction Approximation, DIA) does not contain an adequate number of degrees of freedom
required to provide accurate representations of nonlinear energy and momentum transfers within the
spectrum. In turn, this creates a need for the wind and wave breaking source terms to play artificial
roles in reproducing much of the behavior observed in turning winds situations and to be calibrated
to include these artificial aspects into the total wave physics. Unfortunately, the wind and breaking
source terms also lack the dimensionality required to represent the physics of wave source terms in
these situations.
This presentation provides comparisons of results from detailed-balance simulations in which the
exact integral is used to represent the nonlinear source Results from these simulations show that the
DIA cannot reproduce key spectral behavior observed in the wave spectra around the world. The
presentation then proceeds to develop new physical bases for both the wind input and wave breaking
source terms. These new source terms are both recast in a fashion which considers the probabilistic
contributions of all waves within the spectrum on wind input and wave breaking.
The new breaking term and wind input terms are then generalized into forms applicable to arbitrary
depth. In this form, the new spectral balance produces an evolutionary spectral form that is, in some
aspects, similar to the TMA spectrum hypothesized in 1985 by Bouws et al.. Comparisons of spectra
produced by a model containing the new set of source terms are compared to observations, with very
encouraging results.
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