6 GENERATION OF
FINITE-ELEMENT NETWORK
CGWAVE requires a two-dimensional (2D) triangular grid network for its finite-
element calculations. Although several grid generation packages are available, they are
not suitable for elliptic coastal wave models for which the size of the elements must be
related to the wave length (which varies with local water depth) for proper resolution. A
semicircular open boundary has to be created for special open boundary treatment, and
reflection coefficients, which may vary from one part of the coastal boundary to another,
are also required as input data for the model. To deal with these special problems,
CGWAVE has been interfaced with the grid-generator associated with the SMS (Surface
water Modeling Systems) flow modeling package. The Engineering Computer Graphics
Laboratory is developing this state-of-the-art package for the US Army Corps of
Engineers at Brigham Young University.
SMS contains a set of 2D hydrodynamic models and a general purpose grid
generation and visualization package.
SMS includes an efficient finite-element grid-
generator.
However, this grid-generator was originally designed for other types of
hydrodynamic models. Three utility programs that help interface CGWAVE with the
SMS grid-generator have been developed for use outside SMS, prior to the full integration
of CGWAVE into SMS. Given a coarse rectangular array of bathymetric data, these
programs generate a wavelength-dependent triangular nodal network (based on the user-
specified resolution, i.e. the number of points per wave length), automatically construct
the semi-circular open boundary, assign reflection coefficients along the coastal
boundaries, eliminate unwanted land points, etc. The resulting grid and boundary data
from SMS are then filtered by another utility program for use by the wave model. The
output from the wave model can be processed and then plotted by using SMS. This makes
model implementation very efficient and allows the user to view a graphic representation
of the solution.
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