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

Instability - mean depth at cell centres

Richard McSherry, modified 8 Years ago.

Instability - mean depth at cell centres

Youngling Posts: 2 Join Date: 2/5/13 Recent Posts
I have noticed that there appears to be an instability when selecting the mean depth at cell centres, rather than the max depth of the four surrounding grid points. I am using a Z scheme, trying to model 3D temperature profiles in a lake - the temperature variation becomes unstable when the water level moves up and down. Has anyone else found this?
The documentation does suggest that using mean depth could have some issues associated with it. I have found that using max depth gives a much better temperature computation, but this scheme isn't well suited to areas with steep bathymetry - the depth is always significantly over-estimated (reducing horizontal cell size is an option, but not practical for me due to prohibitive run times).
Thanks in advance for any advice.
Adri Mourits, modified 8 Years ago.

RE: Instability - mean depth at cell centres (Answer)

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

Most important issue: Please switch to the recently tagged version This contains very thorough Z-model updates.

If that is not enough: Try adding the following two lines to the mdf-file (and remove other Trasol/Momsol lines):
Trasol= #iupw#
Momsol= #iupw#

This switches on some more implicit algorithms.


Richard McSherry, modified 8 Years ago.

RE: Instability - mean depth at cell centres

Youngling Posts: 2 Join Date: 2/5/13 Recent Posts
Hi Adri,
Thanks very much for the reply. I am presently trying to compile the new version and will test your suggestions.
Thanks again,