Definition of the gridsDefinition of the grids
Model Definition grid 540 (435x175)Model Definition grid 540 (435x175)
165°40 'E 166°00 'E 166°20 'E 166°40 'E 167°00 'E 167°20 'E 167°40 'E
22°50 'S
22°30 'S
22°10 'S
21°50 'S
W eather station
AD C P C urrentm eterTidegaugeD rifter
167°00 'E
Model Definition grid 180 (200x180)
Phase of ValidationPhase of Validation
0,3
0,35
0,4
0,45
T158 T229 T21 T22 T421 T24 T90
Am
plitu
de (m
)
195
200
205
210
215
220
225
230
235
240
Pha
se (°
g)
Amplitude (données)Amplitude (modèle)Phase (données)Phase (modèle)
0.395
0.40
00.370
0.360
0.350
0.345
0.340
0.340
0.330
0.325
0.330
165°40'E 166°00'E 166°20'E 166°40'E 167°00'E 167°20'E 167°40'E
22°50'S
22°30'S
22°10'S
21°50'S
1 cm 1 cm
Marégraphe < MARS3D Marégraphe > MARS3D
0.32
0.37
0.41
Validation Tide sea surface elevationValidation Tide sea surface elevation
Validation sea surface elevationValidation sea surface elevation
Validation Total currentsValidation Total currents
Validation Total currentsValidation Total currents
Drifter comparison
Drifter : velocity comparison
Examples of resultsExamples of results
1. Current evolution1. Current evolution
2. Residence times2. Residence times
Lagrangian TracorsLagrangian Tracors
Simulation without tide
Evolution of the concentration in 1 point
(example)
0.
0.1
0.2
0.3
0.5
0.6
0.7
0.8
0.9
1.0
0 10 20 30 40 50 60 70 80 90
locale-flushing time
1/e
Flushing lagconcentration evolutionthreshold passing exponential regression fitting the threshold passing curve
Con
cen
trati
on
Time elapsed (days)
0.95
e-flushing time2. Residence times2. Residence times
Method: concentration of one tracer
Case : trade wind de 8 m/s + marée
166°20'E 166°30'E 166°40'E
22°20'S
(days)
> 60
30 - 35
10 - 15
< 0.2
1 - 2
5 - 6
Jouon, Douillet, Ouillon & Fraunié, 2006, Continental Shelf Research, 26, 1395-1415
2. Residence times2. Residence times
3. Dissolved transport3. Dissolved transportTideTideBottomBottom
3. Dissolved transport3. Dissolved transportTideTideSurfaceSurface
3. Dissolved transport3. Dissolved transportTrade WTrade WBottomBottom
3. Dissolved transport3. Dissolved transportTideTideBottomBottom
Mathematical modelGeneral equation of suspended particle transport
4
zCK
3
yC +
xCK =
2
zCsWw +
1
yvC +
xuC +
tC
2z
2
2
2
2h
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 0surface
CsWzCzK
In
Out 0nC
givenC
4. Particle Dynamics4. Particle Dynamics
4. Particle Dynamics4. Particle Dynamics
cd, ce : critical shear stresses for deposition and erosionke : erosion rate coefficient
Mathematical model : cohesive particles (Mud)Fall velocity (Ds < 100 m) :
Stokes’ formula 2
ss D g 1s181W
where
water
particles
Bottom boundary condition EDbottom
Cs
Wz
Cz
K
where : shear stress provided by hydrodynamic modelling
Deposition (Krone, 1962)
Erosion (Parthéniades, 1965)
cdcd
s when CWD
1
cd when 0D
ce when 0E
cd, ce : critical shear stresses for deposition and erosionke : erosion rate coefficient
cece
e n whe kE
1
Application to the southwest lagoon of New Caledonia : Particle Diameter
20151050 km
22°20'S
22°30'S
166°25'E 166°45'E
Coral Sea
166°15'E
NEW CALEDONIA
Grey sand bottoms
White sand bottoms
Muddy bottomsN
OU
MEA
3 coarse kinds of sea bottom (Chardy et al., 1988)
100101 1000
7 m
40 m
Ex: Dumbea Bay
4. Particle Dynamics4. Particle Dynamics
4. Particle Dynamics4. Particle DynamicsApplication to the southwest lagoon of New Caledonia: Calibration
101
100
10-1
10-2
10-3
10-4
0 20 40 60 80 100
max
moy
Pourcentage de vase
(P
a)
0.017
Estimate of a global critical shear stress under tide + trade wind forcings
% of mud
averaged
Example : Deposition after one tidal cycle
166°10'E 166°20'E 166°30'E 166°40'E
22°20'S
22°30'S0.5
0.0
1.0
Deposition
166°10'E 166°20'E 166°30'E 166°40'E
22°20'S
22°30'S
90%
90%
70%
50%
40%
30%
20%
10%
5%
70%
50%
40%
30%
20%
10%
5%
-
-
-
-
-
-
-
<
>
SIMULATIONTide + Trade wind 8 m/s Percentage of mud
Reference : Douillet, Ouillon & Cordier, 2001, Coral Reefs, 20, 361-372
4. Particle Dynamics4. Particle Dynamics
4. Particle Dynamics4. Particle Dynamics
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