AARHUSUNIVERSITET

FlexSimJanus Larsen

20111

•The task

•The solution

•HDLite

•FlexSim

•Horsens fjord

FlexSim - a simple but flexible tool for ecological fjord modeling.

AARHUSUNIVERSITET

FlexSimJanus Larsen

2011

The task›Make a modeling tool to: › estimate fjord modification of loads from the Danish

watersheds in different scenarios› assess the ecological state in Danish fjords in different

scenarios

›The tool must be:› easy to implement on new fjords› have computational times in the order of minutes for

yearly simulations

›Wish list:› Decouple physics and biology› Separate biological and programming expertise

AARHUSUNIVERSITET

FlexSimJanus Larsen

2011

The solution›FlexSIM› Model setup including the ecological equation system is inputted to a

precompiled model engine.› Highly flexible enabling both very fast ‘box’ setups and high resolution 3D

computational grids.

›HDLite: Combined box model-3D model concept

› Water volumes are exchanged between cells as in a box model› Fluxes between boxes are automatically calculated from the computational

grid geometry and simple physical assumptions:› Stratification is created by freshwater runoff in the surface and penetration of

denser salt water from the open boundaries by horizontal mixing.› Stratification is eroded by wind induced vertical mixing.› The timestep is limited only by the size of the cells and the mixing

coefficients

AARHUSUNIVERSITET

FlexSimJanus Larsen

2011

Horsens fjordBathymetry

AARHUSUNIVERSITET

FlexSimJanus Larsen

2011

Horsens fjordSalinity

Course box model 1 year HDLite only in ~10 sec.

Timestep = 3600 sec.

Mixed mesh model1 year HDLite only in <10 min.

Timestep = 120 sec.

AARHUSUNIVERSITET

FlexSimJanus Larsen

2011

Modeling without programming…1. Copy the model engine executable to your windoze computer2. Use a text editor to create or modify mesh, bathymetry and setup files3. Run the engine from the command prompt with your setup file as input

AARHUSUNIVERSITET

FlexSimJanus Larsen

2011

AARHUSUNIVERSITET

FlexSimJanus Larsen

2011