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

Water loss through boundary

Johnny Coyle, modified 4 Years ago.

Water loss through boundary

Youngling Posts: 1 Join Date: 11/17/16 Recent Posts
Hi all

I am wondering if you can help I have built a model of a tidal harbor with inputs along west and the north east section of the model domain. During model calibration the model runs ok for the initial week then an instability develops where two Neumann boundaries meet. This then causes significant drop in water level at the model edge and other instabilities which spread to cover a large proportion of the domain. DA velocity shows water flow from Inflow boundaries exiting the domain through the Neumann boundaries close to this location. I am in the process of formal model calibration and running different permutations of roughness and this instability only appears for one of the permutations of bed roughness. Boundary conditions are identical.

Has anyone encountered this before? It is causing significant water loss from the domain and am wondering how best to resolve this as it is causing significant water loss from the model domain