1. AARHUS UNIVERSITET FlexSim Janus Larsen 2011 1 The task The solution HDLite FlexSim Horsens fjord FlexSim - a simple but flexible tool for ecological fjord modeling.

2. AARHUS UNIVERSITET FlexSim Janus 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

3. AARHUS UNIVERSITET FlexSim Janus 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

4. AARHUS UNIVERSITET FlexSim Janus Larsen 2011 Horsens fjord Bathymetry

5. AARHUS UNIVERSITET FlexSim Janus Larsen 2011 Horsens fjord Salinity Course box model 1 year HDLite only in ~10 sec. Timestep = 3600 sec. Mixed mesh model 1 year HDLite only in <10 min. Timestep = 120 sec.

6. AARHUS UNIVERSITET FlexSim Janus Larsen 2011 Modeling without programming… 1. Copy the model engine executable to your windoze computer 2. Use a text editor to create or modify mesh, bathymetry and setup files 3. Run the engine from the command prompt with your setup file as input

7. AARHUS UNIVERSITET FlexSim Janus Larsen 2011

8. AARHUS UNIVERSITET FlexSim Janus Larsen 2011