After carrying out computations for 10 time-steps, the program displays an
estimate of the run time. The run time could vary, however, depending on other
processes running on the computer at the same time.
Time Series Data Analysis
BOUSS-2D outputs the significant wave height and mean current distribution
over the entire computational grid. For some applications, it might be necessary
to analyze the time series data at specific grid points to obtain frequency or direc-
tional wave spectra, wave height statistics, reflection coefficients, etc. Hughes
(1993) extensively discusses time and frequency domain analysis techniques for
time series data in a laboratory setting. Similar techniques can be applied to time
series output from the numerical model.
Standard statistical analysis techniques can be applied to the surface eleva-
tion or velocity time records to obtain the mean, standard deviation, skewness,
and kurtosis of the time records. The skewness of the surface elevation, η, and its
time derivative, ηt, can be used to quantify the degree of wave asymmetry or
nonlinearity in shallow water. Zero-crossing analysis techniques can be used to
define the heights and periods of individual wave cycles within an irregular wave
record. These can be analyzed to obtain parameters such as the root-mean-square
wave height, Hrms, average height of the highest one-third of the waves, H1/3, or
the average wave period, Tav.
Standard spectral analysis techniques can be used to obtain the surface eleva-
tion or velocity spectra. These can be analyzed to obtain parameters such as the
significant wave height, Hmo, and spectral peak period, Tp. Different techniques
have been proposed for the estimation of directional wave spectra using either an
array of wave gauges (e.g., Nwogu 1989) or collocated measurements of the
surface elevation and horizontal velocities (e.g., Nwogu et al. 1987). Collocated
time series of the surface elevation and horizontal velocities can also be used to
estimate the reflection coefficients using the technique described in Hughes
(1993).
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Chapter 4 Setting Up and Running BOUSS-2D
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