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


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Limiters for spectral velocities: possible in SWAN, but in Delft3D?

Simone Speltoni, modified 1 Year ago.

Limiters for spectral velocities: possible in SWAN, but in Delft3D?

Youngling Posts: 3 Join Date: 6/17/19 Recent Posts
Hallo Community, I have a question about the chance to set limiters for spectral velocities. I'm using Delft3D (Wave standalone module) on a small area of the western Irish coast, on which I make some simulations of energy transport from some buoy's data. By reading this article (, that explains how to set limiters based on CFL condition if submerged mounds with steep  bathymetric gradients are present) I would like to set these limiters in Delft3D too. Does anyone know whether is it possible or not (by adding any keyword in the .mdw file maybe)?
In my case simulations are quite simple (stationary mode, no ambient current, which means that I should need a limiter just for directional- velocity C_lambda); some steep gradients in my bathymetry create a weird (probably unrealistic) peak of energy transport. In SWAN it's possible to set the commands "ctheta" and "csigma" for this purpose, and/or changing the spectral resolution to fix the inaccuracy. Does Delft3d offer the same chance, or can I just adapt the grid resolution?Any help would be welcome! I'm not an expert of Delft3d so apologize if I'm missing something obvious.
Cheers, Simone