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

Neumann Boundary Condition

Fernando Barreto, modified 3 Years ago.

Neumann Boundary Condition

Padawan Posts: 74 Join Date: 6/21/12 Recent Posts
Hi Delft3d Forum,

I'd like to know when we use Neumann BC for WL, which BC Delft3D uses for U and V velocity ? Is it 0 gradient by default?


Adri Mourits, modified 3 Years ago.

RE: Neumann Boundary Condition

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

Section Open boundary conditions in the manual contains information on Neumann boundaries. Does that help?


Samuel Schroers, modified 2 Years ago.

RE: Neumann Boundary Condition

Youngling Posts: 7 Join Date: 9/29/17 Recent Posts

I would like to know about the details a little bit more as well... specifically what is meant by "Beginn" and "End" (see screenshot attached). As Neuman means that a derivative is forced to the open boundary - in my case the derivative would be 2/1 = 2 ?