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


Kaio Lacerda, modified 6 Years ago.


Youngling Posts: 2 Join Date: 5/13/14 Recent Posts
Hi everybody,
I'm trying to apply domain decompostition using two domains and two DD-boundaries to the communication between the domains,
however it blows up after a few time steps and I get the error message:

*** ERROR Water level change too high > 25.00 m (per 0.5 DT) after 226 timesteps in the following points:
(m,n) = (32,244), s0, s1, abs(s0-s1): -0.413E-01 , 0.337E+02 , 0.338E+02
*** ERROR Flow exited abnormally

The corresponding point is one of the points where the DD-boundary was applied at the left domain (Figure1).
At one of the DD-boundaries there's horizontal grid refinemente at 1-to-3,
and at the other there's no refinement. There's no refinement at vertical, it's 2DH.
The grids are of the same type, Cartesian co-ordinates, and I check the grids to make
shure that the grid orientation is the same. I also try to run with constant depth, and it steel blows up.
I ran the domains separately, and they worked well.

I attached the tri-diag files and a figure of the Domain Decomposition (Figure1) to see if somebody can help me.


Kaio Lacerda
Renan Ribeiro, modified 6 Years ago.


Padawan Posts: 55 Join Date: 3/23/11 Recent Posts
Hi Kaio,

Did you try to reduce the time step? And what about the courant number, is it less than 10?