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

BUG - predefined number of subdomains in the source code

Chennakesava Kadapa, modified 1 Year ago.

BUG - predefined number of subdomains in the source code

Youngling Posts: 1 Join Date: 6/13/19 Recent Posts


I found two bugs in the Delft3d source that cause the simulation to crash when running with more than the predefined number of processors/subdomains in the source code.

1.) The first bug is at

character(80), dimension(25) :: subdom_names

in the src/engines_gpl/wave/packages/data/src/flow_data.f90. Because of this one can't run a simulation with more than 25 processors.


2.) The second bug surfaced when running the simulation with 80 cores on multiple (2) nodes on our cluster, Sunbird. This bug is due to

integer, parameter :: max_num_subdoms = 50 ! max # subdomains

in the source file ./utils_lgpl/delftio/packages/delftio/src/delftio_sync/sync_flowwave.f90.


I suggest converting these variables into dynamic arrays.


I hope you can fix these bugs in the future releases.


Best Regards,