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General Description of coastal hydrodynamic model
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Bathymetry Tide Mesoscale circulation Wind Currents Turbulence Sediment transport Mud Model Sand Model Waves WAVEWATCH III l -> k-l, k- WRF Characteristic of a coastal Hydrodymic model
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Equations
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Numerical Formulation
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Necessity of the data and measurements A coastal model must represent the reality as soon as possible. It’s link to the other objectives developed on the study area. From the different point of view we need: Define the forcing Collecting existing data Initiate a strategy of measurement
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Bathymetry
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Currentmeter moorings Meteorological stations Doppler profiling CTD profiling Wavemeter Tide recorders Example of strategy of measurement
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Tide analysis from tidegauge Amplitude in m. Phase in degree
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Tide analysis from classical currentmeters Amplitude in m.
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Wind measurement and analysis of the frequencies
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ADCP currents meters
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Drifters
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Definition of the grids
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Model Definition grid 540 (435x175)
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Model Definition grid 180 (200x180)
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Phase of Validation
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Validation Tide sea surface elevation
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Validation sea surface elevation
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Validation Total currents
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Drifter comparison
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Drifter : velocity comparison
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Examples of results
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1. Current evolution
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2. Residence times Lagrangian Tracors
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Simulation without tide Evolution of the concentration in 1 point (example) e-flushing time 2. Residence times Method: concentration of one tracer Case : trade wind de 8 m/s + marée
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Jouon, Douillet, Ouillon & Fraunié, 2006, Continental Shelf Research, 26, 1395-1415 2. Residence times
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3. Dissolved transport TideBottom
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TideSurface
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Trade W Bottom
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3. Dissolved transport TideBottom
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Mathematical model General equation of suspended particle transport C : Suspended Sediment Concentration of a given grain size / population u, v, w : water velocity provided by the hydrodynamic model Kh : horizontal diffusivity Kz : vertical diffusivity from kinematic turbulent viscosity Open boundary conditions Surface boundary conditions In Out 4. Particle Dynamics
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cd, ce : critical shear stresses for deposition and erosion k e : erosion rate coefficient Mathematical model : cohesive particles (Mud) Fall velocity (D s < 100 m) : Stokes’ formula where Bottom boundary condition where : shear stress provided by hydrodynamic modelling Deposition (Krone, 1962) Erosion (Parthéniades, 1965) cd, ce : critical shear stresses for deposition and erosion k e : erosion rate coefficient
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Application to the southwest lagoon of New Caledonia : Particle Diameter 3 coarse kinds of sea bottom (Chardy et al., 1988) Ex: Dumbea Bay 4. Particle Dynamics
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Application to the southwest lagoon of New Caledonia: Calibration Estimate of a global critical shear stress under tide + trade wind forcings % of mud averaged
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Example : Deposition after one tidal cycle SIMULATION Tide + Trade wind 8 m/s Percentage of mud Reference : Douillet, Ouillon & Cordier, 2001, Coral Reefs, 20, 361-372 4. Particle Dynamics
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