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

Bad Wave Height at Boundaries with Spectral Input. Coupled FLOW-WAVE model

Robert Jenkins, modified 4 Years ago.

Bad Wave Height at Boundaries with Spectral Input. Coupled FLOW-WAVE model

Youngling Posts: 11 Join Date: 7/28/15 Recent Posts
Hi All,

I have been developing a coupled FLOW-WAVE which has a detailed grid nested within a broader coarse grid. And I'm having some trouble with wave spectral boundary input, and bad results at the boundaries.

I handle FLOW nesting with the nesthd1 and nesthd2 tools, with good results.

WAVE nesting is handled by outputting 2D spectra at points, (I use the same observation points as produced by the nesthd1 tool), and then combining spectra files into a single waves.bnd input.

In the MDW file I use the following command to set spectral time series input to the detailed grid:

Name = Boundary1
Definition = fromsp2file
OverallSpecfile = wavesxm01.bnd

Spectral input files look all normal. Output from the coarse grid is normal. Boundary points, I believe and have tested, occur exactly at points on the detailed grid.
The swn-diag file does report some warnings, but these are at points unrelated to the regions that give me issue.

Two examples of my wave results are attached for two grids along with the location of my boundary points. Has anyone seen this issue before?

Chloe Sarah Sarah Morris, modified 9 Months ago.

RE: Bad Wave Height at Boundaries with Spectral Input. Coupled FLOW-WAVE mo

Youngling Posts: 7 Join Date: 1/15/19 Recent Posts
Hi Robert,I am having similar problems (see thread here) and have not been able to find an answer. Did you get any further with this?Thanks,