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

VERY slow computation!

Erin King, modified 2 Years ago.

VERY slow computation!

Youngling Posts: 12 Join Date: 10/5/16 Recent Posts

I have recently started using Delft3D on a new PC which should provide performance gains over my current one. However this has only proved partly true. When running my model domain at 4km wave resolution the performance is better on the new PC. When running at 1km resolution the new PC slows down massively to the point where it is almost 10x slower on the new machine versus the old one! (both running the 1km model).

The idea behind the new PC was partly to allow us to move up to 1km resolution with the waves and so this is a problem.

The slow down appears to be in the Wait (ext. modules) section on the Performance timers output in the tri-diag files (see the images attached). I believe that is just reflecting that the slow down is in the wave computation which is visually apparent watching the iterations.

The new machine has an 8 core CPU with 16 threads VS a 6 core CPU. I have tried reducing the number of threads used by SWAN on the new PC, which speeds up the computation time marginally (enough to run the tests shown in the pictures) but the problem remains.

The new machine is Windows 10 VS Windows 7 on the old machine. Could it be an OS issue?

Any help or experience shared will be appreciated!