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Janus Larsen
Karen Timmermann
Christian Mohn
FlexSim
3D Ecological modelling made user friendly
The modeling framework FlexSim is a fast, flexible and
very user friendly tool specifically targeted towards
scientific and management challenges of the complex
biogeochemical processes in coastal zone ecosystems.
FlexSim is a modular marine modeling framework,
which contains a simplified formulation of estuarine
hydrodynamics and more complex descriptions of
pelagic and benthic biogeochemical processes. It has a
very short computational time and can be easily adapted
to different areas.
FlexSim allows the user to set up computational grids of different complexity ranging from simple box model
configurations to high-resolution unstructured grids. It can be applied by non-experts after a short introduction
and might therefore be a good candidate to support managers and scientists without the need of an extensive
computing infrastructure. Prototypes of FlexSim have been successfully tested for several Danish estuaries.
Here, we present FlexSim and modeling results of the physical conditions in Horsens Fjord, an estuary on the
east coast of Jutland, Denmark. Model simulations were carried out for different scenarios based on varying
complexity of grid geometry and resolution. The model results were compared with observations from the
Danish National Monitoring Programme.
HD model
results
Observed (points) and
modeled (lines) surface
(full/filled) and bottom
salinity (dashed/open) 2004
time series for the box
model setup and highresolution unstructured
mesh configuration. 2004
forcing data for wind speed
and fresh water volume
discharge through the
rivers are shown in the
bottom plot.
Tracing the source
water
A tracer was added to the model. First of
Feb, May, Aug and Nov it was set to 1 for
24 hours. The plot to the left show the
tracer concentration near the source and
near the boundary in the following days.
The peak concentration at the boundary
occurs 2-8 days after tracer release,
depending on the amount of fresh water
run-off in period. Below the Feb event is
depicted as an animation with the surface
concentration at the top and a section
from source to boundary at the bottom.
Computational grids
Computational grids and bathymetry in color
codes for Horsens Fjord used in this study.
Erosion and
build-up of
stratification
Snapshot of surface
salinity and position of
transect of the vertical
section shown in the
figures below. Vertical
salinity distribution as a
response to individual
wind forcing conditions
(indicated by the blue
vertical line in the wind
speed time series above
each figure).
Future and Funding
FlexSIM has been developed by the Baltic Nest
Institute (BNI) at Department of Bioscience,
Aarhus University. We are currently applying for
additional funding to continue developing the
system.
The development plans include support for
decoupling pelagic and benthic ecological
models from full 3D hydrodynamic model fields
provided by any hydrodynamic model, further
refinement of the implemented ecological model
templates and implementation of 3D benthic
models.