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

Nesting a grid with nesthd1

Holly Watson, modified 4 Years ago.

Nesting a grid with nesthd1

Youngling Posts: 1 Join Date: 12/9/15 Recent Posts

I am new to the delft software and have an issue using the NestHD1 tool.

I am currently developing a 2D hydrodynamic model on a rectangular grid in Delft3D FLOW. I am wanting to nest a smaller grid inside my larger calibrated model to have a better resolution in a channel area. The issue I am having is with the creation of the .obs file in the NestHD1 tool that is used to create the boundaries for the nested grid.
I have made the smaller grid and the accompanying enclosure file in RGFGRID. Under the grid there are no changes to the bathymetry or initial variables so I did not interpolate any depths for this nested grid. In the flow GUI I loaded just the smaller nested grid and specified the location of the three boundaries (as I can not do this in the larger grid as they are in the middle of the model) and saved the .bnd file; this file is only a location and has no conditions specified as they are unknown.
In the NestHD1 tool all of the files are accepted, but the .obs file that is created has no data in it and will not open when I try to complete the next stage which is running the larger model with the nested obs file.

Is there any reason that this could be happening? Are the files I am using needed to identify the problem?

Also a question for after I am able to nest a grid. Once the grid is nested, are any changes to the depth file (dredging and wharves are to be added) going to be able to be made with the nested grid boundaries specified for pre work conditions? Or will the larger model and new depths need to be run and new boundary conditions created after each alteration made?

Thank you for your help
Holly Watson
Adri Mourits, modified 4 Years ago.

RE: Nesting a grid with nesthd1

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

Can you zip your input files and attach that to a post on this forum? Ideally, you have simplified your model as much as possible, while still showing the problem.



Gillang Noor Nugrahaning Gusti, modified 1 Month ago.

RE: Nesting a grid with nesthd1

Youngling Posts: 2 Join Date: 3/22/16 Recent Posts
Hi Adri,
I encountered the same problem that the .obs file that was created by NESTHD1 have no data in it. Here I attach the input files, could you please have a check?
Thank you in advance~