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

Numerical parameters

Ana Mioc, modified 7 Years ago.

Numerical parameters

Youngling Posts: 13 Join Date: 7/26/12 Recent Posts
Hi everyone,

Currently I am working on a river model trying to simulate a flood wave that occurred last year.
During the flood the levee was overflowed.
The problem is that depending what numerical parameters (NP) I am using I get different results, meaning the amount of water (m3/s) that went over the levee and time when overflow occurs .
I have read about NP in the manual and I am trying to find the ?right combination? for this type of modeling (I am sure about time when the overflow occurred but not in the amount of water).
I would very much appreciate if someone would share their experience with models like this.

With kind regards,

Arnold van Rooijen, modified 7 Years ago.

RE: Numerical parameters

Hi Ana,

Could you give a small overview of which numerical parameters you changed and what the effect of the change was?

I think most people keep the numerical parameters set to the default values by the way, although in case of drying/flooding issues you could consider changing the threshold depth for instance. But I think more important than the numerical parameters would be your computational timestep (in combination with your grid resolution). Did you try a smaller timestep with identical settings to see whether you get the same results?