The U.S. Army Corps of
Engineers (USACE) maintains a large number of navigation structures in support
of federal navigation projects nationwide. These structures constrain currents
to promote scouring of the navigation channel, stabilize the location of the
inlet channel and entrance, and provide wave protection to vessels transiting
the navigation channel. Such structures are subject to degradation from the
continual impact of currents and waves impinging upon them. Questions arise
about the necessity and
consequences of
engineering actions taken to rehabilitate or modify the structures. A ong-range maintenance and rehabilitation plan
to manage navigation structures and support the federal navigation projects
requires a life-cycle forecast of waves and currents in District projects along
with a quantification of potential evolutionary changes in wave climates
decadally with impacts to analyses and decisions.
The Coastal Inlets
Research Program (CIRP) of the U.S. Army Engineer Research and Development Center
(ERDC) operates a Coastal Modeling System (CMS) that has established and
maintained multidimensional numerical models integrated to simulate waves,
currents, water level, sediment transport, and morphology change in the coastal
zone. Emphasis is on navigation channel performance and sediment management for
inlets, adjacent beaches, and estuaries. The CMS is verified with field and
laboratory data and provided within a user-friendly interface running in the
Surface-Water Modeling System (SMS).
CMS-Wave (Lin et al.
2006b, Demirbilek et al. 2007), previously called WABED (Wave-Action Balance
Equation Diffraction), is a twodimensional (2D) spectral wave model formulated
from a parabolic approximation equation (Mase et al. 2005a) with energy
dissipation and diffraction terms. It simulates a steady-state spectral
transformation of
directional random
waves co-existing with ambient currents in the coastal zone. The model operates
on a coastal half-plane, implying waves can propagate only from the seaward
boundary toward shore. It includes features such as wave generation, wave
reflection, and bottom frictional dissipation.
CMS-Wave validation and
examples shown in this report indicate that the
model is applicable for
propagation of random waves over complicated bathymetry and nearshore where
wave refraction, diffraction, reflection, shoaling, and breaking simultaneously
act at inlets. This report presents general features, formulation, and
capabilities of CMS-Wave Version 1.9. It identifies basic components of the model,
model input and output, and provides application guidelines.
New features added to CMS-Wave
Specific improvements
were made to CMS-Wave in four areas: wave breaking and dissipation, wave
diffraction and reflection, wave-current interaction, and wave generation and
growth. Wave diffraction terms are included in the governing equations
following the method of Mase et al. (2005a). Four different depth-limiting wave
breaking formulas can be selected as options including the interaction with a
current. The wavecurrent interaction is calculated based on the dispersion
relationship including wave blocking by an opposing current (Larson and Kraus
2002). Wave generation and whitecapping dissipation are based on the
parameterization source term and calibration using field data (Lin and Lin
2004a and b, 2006b). Bottom friction loss is estimated based on the classical
drag law formula (Collins 1972).
Other useful features
in CMS-Wave include grid nesting capability, variable rectangular cells, wave
overtopping, wave runup on beach face, and assimilation for full-plane wave
generation. More features such as the nonlinear wave-wave interaction and an
unstructured grid are presently under investigation.
CMS-Wave prediction
capability has been examined by comparison to comprehensive laboratory data
(Lin et al. 2006b). More evaluation of the model performance is presented in
this report for two additional laboratory data sets. The first laboratory data
set is from experiments representing random wave shoaling and breaking with
steady ebb current around an idealized inlet (Smith et al. 1998), covering a
range of wave and current parameters. This data set is examined here in
evaluation of wave dissipation formulations for current-induced wave breaking.
The second laboratory data set is from experiments for random wave
transformation accompanied with breaking over a coast with complicated
bathymetry and strong wave-induced nearshore currents. Comparisons of
measurements and calculations are used to (a) validate the predictive accuracy
of CMS-Wave, (b) investigate the behavior of different current and depthlimited
wave breaking formulas, and (c) select formulas best suitable for spectral
models in nearshore applications. The diffraction calculations by CMS-Wave are
tested for a gap between two breakwaters and behind a breakwater.
CMS-Wave Interface
Demirbilek et al.
(2007) described the computer graphical interface in the SMS (Zundel 2006) for
CMS-Wave applications. A summary of key features of the interface is provided
in this chapter to familiarize users with guidelines for the interface usage
and implementation of CMS-Wave. The SMS is a graphically interactive computer
program designed to facilitate the operation of numerical models and creates
input files and output visualization for CMS-Wave. The CMS-Wave interface in
the SMS is similar to that of the half-plane model of STWAVE Version 5.4 (Smith
2001b). The SMS can generate CMS grids with variable rectangle cells and
half-plane STWAVE grids with constant square cells. Both wave models can use
the same grid domain with identical grid orientation and layout, and the same
file formats for their bathymetric and spectral energy files. This was done to
facilitate the usage of CMS-Wave and allow users to utilize the same settings and
files to run both models without modifications.
CMS-Wave files
Depending on which options
are selected in the *.std file, CMS-Wave may generate one to six output files.
A wave field conditions file (*.wav) is always generated. Optional output files
are calculated spectra (*.obs) and wave parameters with the maximum water level
(selhts.out) at selected cells, wave breaking indices (*.brk), wave radiation
stress gradients (*.rad), wave setup and maximum water level field (setup.wav),
and nesting spectral data (*.nst). Figure 1 shows a chart of input and output files
involved in a CMS-Wave simulation. Table 1 presents a list of the type and use
of all I/O files, where “projname” is a prefix given by users.
The simulation file
(*.sim) stores the coordinates of the origin and orientation of the
computational grid, and a list of names of all files used in the simulation.
All input and output files, required and optional, are listed in Figure 1 and
is described in Table 1. Abbreviated output from sample files was provided in
Technical Note ERDC/CHL CHETN-I-74 (Demirbilek et al. 2007) and presented in
Appendix A to familiarize users with these files.
Users can run CMS-Wave
with the input files of STWAVE Version 5.4 without making changes. In this
case, CMS-Wave runs in a basic mode. Although doing this may be useful in some
project applications, the basic mode does not take advantage of certain
features of CMS-Wave, such as reflection. Users should run CMS-Wave with its
special set of parameters as defined in the *.std file. That is, one can edit
*.std, without modifying *.sim and *.dep, to add a few additional parameters
that are specific to CMS-Wave. Guidance on various parameters and recommended
values is given below.
File used simulation
Users can provide up to 15 control parameters in the *.std. They
are (in
sequential orders) iprp, icur, ibrk, irs, kout, ibnd, iwet, ibf, iark, iarkr,
akap, bf, ark, arkr, iwvbk, which represent:
|
iprp
|
= 0, for wave generation and propagation (use
wind input if
provided)
|
= 1, for propagation only (neglect wind input)
= -1, for fast-mode simulation (for wave generation and
propagation)
icur = 0, no current
= 1, with current input (*.cur), using data sets in the sequential
order
= 2, with current input (*.cur), using only the first set current data
|
ibrk
|
= 0 (no *.brk file)
= 1, for output of wave breaking indices (*.brk)
= 2, for output of energy dissipation fluxes (*.brk)
= 0 (no *.rad file)
|
|
irs
|
|
= 1, for output of wave radiation stresses (*.rad)
= 2, for output of wave radiation stresses (*.rad) and wave setup/maximum water
level (setup.wav) kout = 0 (no *.obs and selhts.out files)
= n, for output of spectra (*.obs) and parameters (selhts.out) at n selected
cells ibnd = 0 (no *.nst file)
= 1, for nested grid, with linear interpolation of boundary input spectra
(*.nst)
= 2, for nested grid, with morphic interpolation of boundary input spectra
(*.nst)
|
iwet
|
= 0, for normal wetting/drying (use water
level input)
= 1, no wetting/drying (neglect water level input)
= 0, no bottom friction
|
|
ibf
|
|
= 1, for bottom friction with constant Darcy-Weisbach type coefficient
(= bf)
= 2, for bottom friction with variable Darcy-Weisbach type coefficient
(friction.dat)
= 3, for bottom friction with constant Manning coefficient (= bf)
= 4, for bottom friction with variable Manning coefficient (friction.dat)
|
iark
|
= 0, no forward reflection
= 1, with forward reflection
|
iarkr = 0, no backward reflection = 1, for backward reflection
akap = diffraction intensity factor (0 for no
diffraction, 4 for strong diffraction)
|
bf
ark
|
= constant bottom friction coefficient
= constant forward reflection coefficient (0 for no reflection, 1 for
maximum forward reflection)
= constant backward reflection coefficient (0 for no reflection, 1 for
maximum backward reflection)
|
|
arkr
|
|
iwvbk = option for selection of wave breaking formula = 0, for
Extended Goda (Sakai et al. 1989) = 1, for Extended Miche (Battjes 1972; Mase
et al. 2005b) = 2, for formula by Battjes and Janssen (1978) = 3, for formula
by Chawla and Kirby (2002)
Users can assign 0 for
15 control parameters in CMS-Wave to run in the basic mode. If only the first
six parameters, iprp, icur, ibrk, irs, kout, and ibnd, are provided (minimum
requirement) in *.std, a zero will be assigned to the remaining parameters,
except that a default value of 1.0 is assigned to the diffraction intensity
factor (akap = 1.0) to simulate a weak diffraction condition. If only the first
ten parameters, iprp, icur, ibrk, irs, kout, ibnd, iwet, ibf, iark, and iarkr,
are provided in *.std (no other information provided for the bottom friction
and reflection coefficients), default values of bf = 0.0, ark = 0.5 (for 50
percent energy forward reflection), arkr = 0.3 (for 30 percent backward energy
reflection), and akap = 1.0 are used by the model. CMS-Wave calculates wave
transmission, wave runup, and overtopping as special features on selected
cells. These cells can represent a floating breakwater, a bottom mound
breakwater, a beach segment and the land adjacent to it, jetties, seawalls, or
underwater features such as reefs or submerged structures. A trench, submerged
mound, or structure can be added to the bed as features without modifying the
input depth file. These feature cells need to be specified in the *.struct file.
Each feature cell is described by four parameters, istruc, jstruc, kstruc, and
cstruc in a line format in the *.struct
istruc = i-th column in
the grid
jstruc = j-th row in
the grid
kstruc = feature cell
identity
= 1, for adding
alternative feature or structure (immersed or
exposed) without
modifying the input depth
= 2, for calculation of
wave runup and overwash on beach face or
structure, and adjacent
land
= 3, for calculation of
transmitted waves of a floating breakwater
= 4, for a vertical
wall breakwater
= 5, for a composite or
rubble-mound breakwater
cstruc = feature
structure depth, for kstruc = 1 (assume a land cell if not
provided)
= beach/structure
elevation above mean water level, for kstruc = 2
(use the input depth if
not provided; no effect for cstruc < 0)
= floating breakwater
draft, for kstruc =3 (skip if not provided or
cstruc < 0.05 m)
= breakwater/structure
elevation, for kstruc = 4 or 5 (use the input
depth if not provided;
immersed if cstruc < 0)
Model Validation
Numerical models are validated
by comparing model calculations to data and analytical solutions to determine
the reliability of a model’s individual or combined features. Data for model
validation come from laboratory and field measurements, whereas analytical solutions
are available in the literature and engineering manuals. Validation tests are essential
benchmarks for evaluating both general features and the unique capabilities of numerical
models.
This chapter describes and
discusses nine examples, or cases, and four depth-limited breaking wave
formulas. The CMS-Wave validation is shown for eight data sets from laboratory
and field studies, two sets of analytical solutions, and two sets of semi-empirical
calculations. The laboratory data are from experiments that have been conducted
for idealized inlets, plain sloping beaches, and jetties. These data are examined
for validation of wave breaking formulas, wave-current interaction, wave runup,
and overall model performance at inlets and nearshore.
Theoretical solutions for wave
diffraction at a semi-infinite breakwater, a single gap, and multiple gaps in
breakwaters are examined to evaluate the reliability of CMS-Wave calculations
for simulating wavestructure interaction problems. The wind-wave growth
capability of CMSWave is validated with semi-empirical relations given in the
U.S Army Corps of Engineers Shore Protection Manual (1984) and Coastal
Engineering Manual (Headquarters (HQ), USACE 2002). The wave reflection
capability of CMS-Wave was tested based on a laboratory experiment conducted
for an idealized inlet protected by dual jetties (Seabergh et al. 2005). Both
fully reflected and absorbing jetties were tested in the experiment. Details of
the experiment, data, and CMSWave predictions and comparisons were summarized
in (Lin et al. 2006b). This Technical Note also includes additional tests comparing
CMS-Wave results to data for wave diffraction around and behind a
shore-parallel breakwater and wave diffraction measurements by Seabergh et al.
(2002)
at the bay side of an inlet
