intro story D-Flow FM


D-Flow Flexible Mesh

D-Flow Flexible Mesh (D-Flow FM) is the new software engine for hydrodynamical simulations on unstructured grids in 1D-2D-3D. Together with the familiar curvilinear meshes from Delft3D 4, the unstructured grid can consist of triangles, pentagons (etc.) and 1D channel networks, all in one single mesh. It combines proven technology from the hydrodynamic engines of Delft3D 4 and SOBEK 2 and adds flexible administration, resulting in:

  • Easier 1D-2D-3D model coupling, intuitive setup of boundary conditions and meteorological forcings (amongst others).
  • More flexible 2D gridding in delta regions, river junctions, harbours, intertidal flats and more.
  • High performance by smart use of multicore architectures, and grid computing clusters.
An overview of the current developments can be found here.
The D-Flow FM - team would be delighted if you would participate in discussions on the generation of meshes, the specification of boundary conditions, the running of computations, and all kinds of other relevant topics. Feel free to share your smart questions and/or brilliant solutions! 


We have launched a new website (still under construction so expect continuous improvements) and a new forum dedicated to Delft3D Flexible Mesh.

Please follow this link to the new forum: 

Post your questions, issues, suggestions, difficulties related to our Delft3D Flexible Mesh Suite on the new forum.





Sub groups
D-Flow Flexible Mesh
Cohesive sediments & muddy systems


Message Boards

Offline wave-flow computations

Joe Long, modified 8 Years ago.

Offline wave-flow computations

Youngling Posts: 2 Join Date: 12/19/11 Recent Posts
We are in the process of trying to implement a large series of coupled WAVE-FLOW computations. Online WAVE-FLOW coupling works fine with our grid/forcings, etc. We would, however; like to implement a large number of scenarios using offline WAVE-FLOW coupling where the coupling is one-way, just stationary wave forcing supplied to the FLOW grid. This can be accomplished by choosing online wave-flow coupling and setting the communication interval to be equal to the simulation time. In that case, WAVE runs at the beginning of the run and again at the end. We would like to avoid running WAVE a second time and setting the interval to be greater than the simulation time does not work (D3D automatically resets it to the length of the simulation).

The other way should be to do offline wave-flow coupling. Doing this we would be able to avoid a second WAVE simulation and run flow using mpi (which we have not been able to do using online coupling; only WAVE uses all processors). Within the Delft3d framework, when doing this we try to run WAVE with WriteCom set to 'true' (so that a com-file will be generated) it will not run because it also wants a com file prior to starting the simulation. With WriteCom='false' WAVE runs and finishes successfully, writes output files, but no com-file. Without a com- file FLOW will not run. If we try to run FLOW first (which is what happens when you do online coupling) it will not run because it wants information from WAVE.

Can you advise on how to accomplish offline WAVE-FLOW coupling within the D3D framework (e.g. other than running SWAN externally, outputting radiation stresses, etc).

Adri Mourits, modified 8 Years ago.

RE: Offline wave-flow computations

Yoda Posts: 1221 Join Date: 1/3/11 Recent Posts
Hi Joe,

Try this:
  • Run FLOW with WAVE online, with a WAVE calculation at the start time and FLOW only performing one time step. When doing this, FLOW will create the com-file and WAVE will add (wave-)data to the com-file.
  • Use the created com-file for FLOW runs without running WAVE online. In FLOW: switch on the wave process, switch off "WAVE online", be sure that the com-file is named "com-<runid>.dat/def", where <runid> exactly matches the name of the mdf-file used ("<runid>.mdf").