A recently developed coupling between FEFLOW® and MIKE 11® (IfmMIKE11) adds new dimensions to integrated ground- and surface water modelling.
DHI Water & Environment and WASY GmbH, Institute for Water Resources Planning and Systems Research are delighted to announce their co-operation in coupling the well known and widely distributed simulation systems FEFLOW® and MIKE 11®.
FEFLOW® is one of the most sophisticated groundwater modelling software packages for complex groundwater flow and contaminant transport problems. The primary components of the FEFLOW® system are interactive graphics, a GIS and CAD interface, advanced mesh generators, data regionalization and visualization tools and powerful numerical techniques, based on the finite-element method. The system allows efficient site-specific setup of the finite-element mesh, quick and easy assignment of complex model properties and boundary conditions, stable and fast simulation, and effective visualization of the results. In addition, the interface is loaded with many advanced features and graphical modelling tools. To extend the capabilities of FEFLOW by user-programmed modules, there is an open programming interface controlled by the Interface Manager (IFM). For further information on FEFLOW see www.feflow.biz or www.feflow.info.
MIKE11 is a software package developed by DHI to simulate complex 1D hydrodynamic flow problems. The software enables the user to simulate unsteady flow in river networks as well as looped networks. Using an implicit finite difference scheme, both sub- and supercritical flow conditions can be simulated. A big advantage of the model is that most of the input parameters can be variable in time (for example K-values). MIKE11 is integrated in the software MIKE ZERO, which functions as a GUI for MIKE 11. For further information on MIKE 11 see www.mike11.com.
With the interface IfmMIKE11 module, based on the FEFLOW Interface Manager IFM both products are now coupled in a user-friendly way. The coupling is made fully dynamic such that the two codes are running simultaneously and thus parallel in time. Water levels of MIKE11 are transferred as boundary conditions (3rd kind) for FEFLOW and exchange discharges between ground water and surface water along the branches calculated by FEFLOW are transferred to the MIKE11 calculation points as lateral inflow/outflow. The assignment of the FEFLOW boundary points to the MIKE 11 calculation points can be specified fully automatically. Further more, a comfortable GUI enables the user to check the assignment being made as well as to observe the interaction while simulating.
Apart from the obvious application of the module in models simulating flooded areas, recent projects showed that the module could also be used while developing pumping strategies for polder areas. In these areas the drainage ditches only divert groundwater. An effective modelling of those ditches, and consequently the pumping strategies of the pumping stations, could therefore only be achieved by a dynamic coupling of the ground and surface water systems.
The module uses the transfer rates module integrated in FEFLOW to determine the leakage coefficient. After each time step in FEFLOW, the length of that time step is simulated by MIKE11 using the actual time step length of MIKE11. The final time step of MIKE11 is reduced in order to fit the actual time of FEFLOW. This approach has been tested successfully. The internal time step length of MIKE 11 can be adapted by setting maximum and minimum allowed changes of the water levels in the model. FEFLOW time steps can be adapted by the options already available in FEFLOW. They are not being influenced by the time steps of MIKE 11.
User-interface of IfmMIKE11
For further information please see www.feflow.de or contact either sales@wasy.de or software@dhi.dk