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

Error initializing Nested FLOW run

Robert Jenkins, modified 5 Years ago.

Error initializing Nested FLOW run

Youngling Posts: 11 Join Date: 7/28/15 Recent Posts
Hi All,

I'm still very new to delft3D
Recently I'm trying to set up a nested FLOW run, and I get the following error while initializing the inner grid.

*** ERROR Nr. of opening points too large.

The overall grid runs fine, and the nesting tools report no issue. So far I've found no documentation on this error message.
Any insight would be great!
Adri Mourits, modified 5 Years ago.

RE: Error initializing Nested FLOW run (Answer)

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

You have too much open boundary points.

The easiest solution is to reduce the number of open boundary points.

The more complex solution is to change the source code:
In file "....\src\engines_gpl\flow2d3d\packages\data\src\allocation\decarr.f90", line 216:
nopest = 4 * (nmax+mmax)

Increase the value of nopest and recompile the source code.

The neat solution is to remove this hard coded maximum for the number of open boundary points. That's on our To Do list.


Shereen Nazer, modified 2 Years ago.

RE: Error initializing Nested FLOW run

Youngling Posts: 4 Join Date: 8/17/18 Recent Posts

hi....can you help me by explaining the procedures for doing the nesting tool in flow module