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Flow modelling
The objective is to set up a 3D model that simulates water
levels and stratified flow in the pilot area (including the Essequibo river
up to Bartica and the Demerara river up to New St. Eustatius) under the
influence of forcing by tide, wind, and river discharge. The main purpose of
the flow model is to provide tools for planning of coastal works and as
boundary conditions for the design of structures.
Extensive studies were carried out in the coastal zone of Guyana in the
period 1960’s and 1970’s by NEDECO/WL | Delft Hydraulics. The present study
will not only make use of the data collected during these studies, but will
review and update the findings resulting from these studies. Were the
1960-1970 studies only based on field observations, the present study is
based on a combination of field observations and numerical modelling. This
being a logical difference in approach between the two era’s. The primary
benefit of using a numerical model above only field observations, is the
fact that a computer model can be run for any period in time and under any
specified environmental condition. Besides, the numerical model can be
updated with additional field observations (e.g. depth, water level or
current measurements) in order to update the model or increase its level of
accuracy.
In the present project the purpose of the numerical 3D flow model is to:
1. assess
the average and extreme water levels and current velocities for e.g. the
design of sea defence structures;
2. assist
in understanding the hydrodynamics at the Guyana coast;
3. provide
a base model for the wave and morphology modelling;
4. train
Guyana engineers in the use of hydrodynamic models.
The model is based on WL | Delft
Hydraulics state-of-the-art programme Delft3D-FLOW.
For more information please go to
http://www.wldelft.nl/soft/d3d/intro/index.html
or click on picture.
In order to make an accurate
representation of the flow conditions in the pilot area, the behaviour of
the tide, ocean currents and river discharges must be well understood and
defined. Therefore, two flow models have been set-up:
1.
a large-scale model – further referred to as overall model -
that simulates the tidal propagation in a wide area around the pilot area as
well as the river discharge. This depth-averaged model covers the entire
coastline of Guyana and part of the coast of Suriname. The rivers are
represented in a schematic way in order to dissipate the tidal wave. The
overall model extends into deep water (>2000m), beyond the continental
shelf. This model was set-up solely to provide tidal and river boundary
conditions for the detailed flow model and does not include ocean or
wind-driven currents. The model is presented
below.
overall tidal model of the Guyana coast
2.
a detailed model covering the pilot area: The model includes
a 250 km wide coastal area centred around the Essequibo river mouth and
extends about 85 km offshore. The Essequibo river up to Bartica and the
Demerara river up to Timehri are included in the detailed model. This model
was set-up both in two-dimensional (depth-averaged) and three-dimensional
mode. The latter including salinity in order to simulate stratified flow.
See computational grid below.
computational grid of the
detailed model
depth schematisation in
Essequibo estuary
A standard procedure of calibration and verification
has been adopted. This procedure is required to ensure that the numerical
computations closely simulate the real flow conditions.
Comparison between measured and
computed water levels
Reproduction of Guyana Current
Animation
showing salinity distribution during a tidal period (.avi,
1Mb)
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