ERDC/CHL CHETN-I-64
September 2001
applications where wave propagation distances are short, wind input may not be required.
For longer propagation distances, strong winds, or cases where locally generated waves
dominate (e.g., bays), the wind input should be included. In typical U.S. East and West
Coast applications, peak tidal currents exceeding 3 ft/sec (1 m/sec) may significantly alter
wave transformation and should be included. The output options include specifying
regions of wave breaking, calculating radiation stresses, and saving wave spectra at
selected output locations. Radiation stresses can be used to calculate wave-driven
more output options or special output points selected, the more disk space required for
model output and computational time to write the output. Two-dimensional fields of
significant wave height, peak period, and mean direction are also saved over the entire
model domain.
Fields of wave height,
Model Parameters
period, and direction
Bathymetry
Spectra at selected
grid cells
STWAVE
Incident wave
spectra, wind,
Fields of radiation
and water level
stress gradients
Fields of breaker
Currents
indices
Figure 3. STWAVE input and output file schematic
b. Bathymetry. The input bathymetry describes the STWAVE grid dimensions and grid
spacing as well as the water depth for each grid cell. The grid must be defined in a flat-
earth coordinate system (e.g., state plane). Water cells are denoted with positive depths
and land cells with negative depths. Lateral grid boundaries can be specified as land (bay
or lake site) or water (open coast site). Water boundaries are assumed to be open and
allow wave energy, consistent with neighboring cells to propagate into or out of the
domain (zero-gradient type boundary condition). Land boundaries allow no energy to
propagate in or out of the domain. The offshore boundary can also be completely or
partially land for local generation cases (bays or lakes).
c. Incident wave spectra, wind, and water levels. The input waves on the offshore grid
boundary are specified as a wave spectrum. Input spectra can be interpolated from the
WIS hindcast, results from another numerical model, or field measurements; or spectra
can be generated based on wave height, period, and direction using standard spectral
shapes. SMS provides tools to generate spectra. The spectral input also includes the
number of frequencies and directions given in the input spectra (and used for all
calculations). The number of directions is fixed at 35 in STWAVE (5-deg resolution).
Smith, Sherlock, and Resio (2001) provide guidance on selecting the number and
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