Billy L Edge amp Margery Overton CVEN 69502 Bathymetric Data Why do we need wave models Wave climate assessment at the project site is important to most coastal amp ocean engineering projects including ID: 713078
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Slide1
Wave Modeling
Local Wave Transformations
Billy L.
Edge & Margery Overton
CVEN 695-02Slide2
Bathymetric
DataSlide3
Why do we need wave models?
Wave climate assessment at the project site is important to most coastal & ocean engineering projects, including
- navigation and channel studies
- on/offloading of ships
- optimization of harbor layouts
- design of structures (breakwaters, etc.)
shoreline erosion projects, etc.
Nearshore
wave conditions are normally determined from deepwater conditions
- long-term
nearshore
wave data are usually unavailable
- transform offshore wave data to
nearshore
(wind-generation, shoaling,
refraction, breaking, dissipation, bottom friction) –
regional scale models
- investigate local scale phenomena (refraction, wave reflection, diffraction,
nonlinear wave-wave and wave-current interaction) –
local scale modelsSlide4
Regional Scale Wave Modeling
Scale O(100 km~5000 km)
Spectral wind-wave models (WAM)
Scale
O(10 km ~100 km)
Spectral wind-wave models (STWAVE and SWAN)
Dominant process: wind input, shoaling and refraction
Wave action: conservation equation
Assume phase-averaged wave properties vary slowly over distances of the order of a wavelength
Cannot
accurately resolve rapid variations that occur at sub-wavelength scale due to wave reflection/diffraction Slide5
Local Scale Wave Modeling
Scale O(1 km ~ 10 km)
Elliptic mild-slope model (CGWAVE)
Parabolic mild-slope model (REFDIF)
Boussinesq wave model (BOUSS-2D)
Dominant processes: shoaling, refraction, breaking, reflection, diffraction, wave nonlinearities due to interactions of different frequencies and ambient currents and structures
All models use vertically integrated eqns for wave propagation in 2D horizontal plane
CGWAVE assumes hyperbolic cosine variation of the velocity potential over depth, and BOUSS-2D assumes a quadratic variationSlide6Slide7
Summary of Model Features
Phase resolving
Phase averaging
Phase averaging
Diffraction/Reflection
Nonlinear Interactions
Wave-Current Interaction
Wave Breaking
Shoaling/Refraction
BOUSS
CGWAVE/
REFDIF
STWAVESlide8
Spectral Wind-Wave Models
Advantages
wind-wave generation
shoaling, refraction, breaking
wave-current interaction
applicable to large domains (deep to shallow water)
Disadvantages
reflection, diffraction
steady-stateSlide9
Elliptic Mild-Slope Models
Advantages
well suited for long-period oscillations
shoaling, refraction, breaking, bottom friction
reflection, diffraction
wave-current interaction (in future version)
flexibility of finite elements
Disadvantages
nonlinear interactions in shallow water (in future version)Slide10
Parabolic Mild-Slope Models
Advantages
shoaling, refraction, breaking, bottom friction
Refraction, reflection, diffraction
wave-current interaction
Disadvantages
Grid limitations in size and regular griddingSlide11
Boussinesq Wave Models
Advantages
shoaling, refraction, breaking, bottom friction
reflection, diffraction, nonlinear interactions
wave-induced currents, wave-current interaction
Disadvantages
computationally intensive
2-D very computationally intensiveSlide12
Applicability
STWAVE:
ideal for wave propagation in open water
SWAN:
time dependent, larger domain
Mild-Slope:
ideal for long-period oscillations in harbors (CGWAVE)
suited for strong diffraction & reflection
more flexibility with finite element method(CGWAVE)
rapid solutions(REFDIF)
BOUSS-2D:
ideal for wave transformation near entrance channels and harbors
nonlinear interactions in shallow water
wave-induced currents near structures and
surfzoneSlide13
Engineering
Practice - 1
CORPS
wave models have good physics to provide reliable estimates to projects
Integrated with tools (
SMS,etc
.)
Used in support of a variety of research and engineering studies
Have strengths & weaknesses – no one model can do it all!
Validated with field/lab data & checked against analytical solutions
MIKE21
wave models …
DELFT3D
wave models …Slide14
Wind forcing
Current forcing
Wave-current
Regional modeling
Deepwater wave transformation up to pre-breaking depths
Finite difference
Spectral, steady state
Quick to run
Good front end
STWAVE computed wave Heights
STWAVESlide15
CGWAVE
Diffraction
Reflection
Refraction
Breaking
Bottom friction
Entrance losses
Finite element mesh
Spectral sea state
Wave-current Interaction (in testing)
Wave-wave Interaction (in testing)
No wind Input
CGWAVE Sea state for Morro Bay, CASlide16
BOUSS-2D
Time-dependent
Open coast, harbor and surf zone waves
Shoaling, refraction, reflection, diffraction,
dissipation and run-up
Finite difference
Random spectral sea state modeling
Wave-induced currents
Nonlinear waves, sub- and super-harmonics
BOUSS-2D Simulation for Everglades projectSlide17
Engineering Practice
-2
Modeling
waves in navigation channels/inlets is most challenging -- need reliable lab & field data to check complex physics of models
WIS data suitable for open-coast, but may be transformed and used in navigation projects
Use STWAVE or SWAN to transform deepwater wind/wave climate to
nearshore
(10 to 30 m) depth contour Slide18
Engineering Practice
-3
Have to use models if no nearshore field data available
Using models that are in common practice and have acceptance in the engineering community is preferred to one of a kind models
Project-specific problems must determine the type of model for a study
Detailed model documentation is necessarySlide19Slide20
Grays Harbor, WashingtonSlide21
Grays Harbor, WashingtonSlide22Slide23
Entrained SandSlide24
Local Wave KinematicsSlide25
Regions of
Application of Wave ModelsSlide26
Solitary/Cnoidal
WavesSlide27
Wave Prediction (Deep Water)Slide28
Combined Refraction and Shoaling
(Dean and Dalrymple)Slide29
Wave DecaySlide30Slide31
Random Waves
Analysis Methods
Eye
ZUC
ZDC
SpectralSlide32
Random Wave Spectra
JONSWAPSlide33
Wave Spectra
TMA
Pierson Moskowitz
Other
JONSWAPSlide34
Mild Slope Equation
http://www.coastal.udel.edu/refdif/img20.htmSlide35
CONCLUSIONS
BOUSS-2D is a powerful nonlinear model for estimating waves in shallow and intermediate water depths where wave diffraction and nonlinearities are important
Model is ready for project applications
SMS interface of BOUSS-2D
MAKE THINGS AS SIMPLE AS POSSIBLE BUT NO SIMPLER!!! – “Albert Einstein”Slide36
REFDIF