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Features
& Benefits ~ Model Description
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Simulated
surface current during maximum
flood with BGS in operation. |
Numerical
modeling is a powerful method of visualizing the dynamic behaviour
of physical systems. We have developed a three-dimensional computer
model (COCIRM-ASL) capable of accurately simulating water circulation
in:
- Rivers
- Estuaries
- Coastal
Waters
- Continental
Shelf and Deeper Waters
Our
model is founded solidly on the science of fluid dynamics for circulation
including such natural forces as:
- Tides
- Density
stratification and buoyancy
- Wind
stress
- Drag
arising from the shoreline and bottom
- Coriolis
The
variable discharge from such engineered works as dams, power stations
and sewage treatment stations can readily be included in the model.
Our model has been fully calibrated and validated through comparison
with extensive data sets in a variety of project environments.
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Features
and Benefits
Simulated
surface current during maximum
flood without BGS in operation. |
Successful
calibration and validation of a numerical model against field measurements
is an affirmation of our understanding of the natural environment
being studied. The power of our computer model "COCIRM-ASL"
lies in its ability to predict currents, temperature, salinity and
sediment in regions where data is sparse or when extensive data
collection is expensive or impractical. COCIRM-ASL can undertake
"what if" studies to investigate the impact on river,
estuarine or coastal circulation patterns of the placement, for
instance, of:
- A new
dam or plant
- The effect
of changing discharge levels or operational configurations.
- Coastal
engineering structure.
For
application of COCIRM-ASL to a new project area, one need only input
the geometry of the modeled domain (shoreline, bathymetry, engineering
structures), open boundary conditions, and physical properties that
are known.
The
distribution and behaviour of key properties can be readily simulated
within the ASL model, including:
- Tidal
currents and circulations
- Temperature,
salinity, and suspended sediment concentration (SSC)
- Bottom
siltation and scour
- Biological
or chemical distributions: plankton abundance, coliform concentrations,
oil spills
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Model
Description
COCIRM-ASL
uses hydrodynamic pressure, sigma-transform, and variety of turbulence
parameters. It solves for the time-dependent, three-dimensional
velocities (u, v, w), temperature(T), salinity(s), SSC(c) as well
as water surface elevation (Jiang, 1999). It also includes wetting/drying
and nested sub-grid schemes, capable of incorporating tidal flats,
buoyant jets and relatively small interested areas.
The
model boundary conditions consist of the momentum flux (wind stress)
at the water surface and the shear stress at the bottom in terms
of quadratic or linear law.
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Domain
Specification |
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| Data
collections (tides, currents, temperature, salinity, SSC &
wind, etc.) |
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Boundary
Conditions |
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Initial
Conditions
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| Model
calibration and validation |
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3D
Model
(COCIRM-ASL) |
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Bathymetry |
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| Selection
of physical processes (horizontal and vertical diffusions,
bottom friction, etc.) |
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Predictions
of currents, temperature, salinity & SSC, etc. |
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At
open boundaries, the water levels, velocities or radiation conditions
are specified. In the case of discharge from a dam, the resulted
currents are oriented to the same direction as the spillway.
A
semi-implicit finite difference method is applied in COCIRM-ASL.
The numerical solution method has the advantages of a minimum
degree of implicitness, good stability (unconditionally stable
when one neglects horizontal diffusion) and consistency, and high
computational efficiency at a low computational cost. Grid sizes
can range from 10 m to kilometers in size.
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