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

Delft3D-SWAN error - Segementation Fault (core dumped)

Nate VanArendonk, modified 3 Years ago.

Delft3D-SWAN error - Segementation Fault (core dumped)

Youngling Posts: 3 Join Date: 2/10/17 Recent Posts
Hi All,

I am having trouble running some of my domains when I increase the resolution of the grid. I am having success when I run my model on my 62.5 meter grid which is a 1157x871 grid. Then when I cut the resolution in half to 32.25 meters with a grid of 2313x1741, I am met with an error while Swan is trying to write output files. Here is what I get:

+SWAN is processing output request 1
Segmentation fault (core dumped)
*** WARNING: unable to run SWAN using "". Trying with "swan.bat" ...
sh: 1: swan.bat: not found
>>...End of SWAN run
*** ERROR: file 'norm_end' expected to signal a correct SWAN calculation

Unfortunately a print file or error file are not created so this is my only clue as to what the error is. I've never encountered a Segmentation Fault (core dumped) error before. A quick internet search revealed that it means Swan is trying to access memory it has not been told it has access too. I am wondering if anyone has encountered an error like this in the past? In an attempt at a quick fix, I upped the available memory to 53 gigs and this did not solve the problem ( the model only uses around 22) I should note that I am running Delft3D-64bit Swan on Linux - Ubuntu through a virtual machine.

I am a little curious why the coarser resolution grid works then when I cut the resolution in half and increase the grid size, it throws this error, with plenty of available memory. If anyone has any suggestions on how I can fix this problem it would be greatly appreciated! Realistically, I do not need to run my models at a resolution of 32.25m however, I have a very large domain at 100 meter resolution which encompasses these smaller domains (grid size is 2438x3541). When I run this model it uses around 48 gigs of RAM and after SWAN is done running and attempting to write the outputs I am met with the same error that I pasted above.

***Summary: I have large domains that I am running on 64-bit Swan on linux. The models run and when swan is attempting to process and write the output files, I am met with an error of "Segmentation Fault (core dumped). Any advice on how to fix this?

Anonymous Anonymous, modified 2 Years ago.

RE: Delft3D-SWAN error - Segementation Fault (core dumped)

Jedi Master Posts: 333 Join Date: 7/30/20 Recent Posts

Dear Nate,

I am facing the same issue with my mesh, as soon as I start increasing the resolution (<50 m) on a coupled flow-wave simulation, SWAN gives me the same error (also running on 64bit Linux in MPI-parallel with plenty of resources). 

Did you find a solution to the problem? I am a little bit puzzled atm.



Anonymous Anonymous, modified 2 Years ago.

RE: Delft3D-SWAN error - Segementation Fault (core dumped)

Jedi Master Posts: 333 Join Date: 7/30/20 Recent Posts

Short update on that note; a further increase in resolution (<20 m) renders the model operational again. However, different resolutions on the different grids FLOW (20x20m) and WAVE (60x60m) seem not to work on the version I am running, hence I have to run both grids at the same resolution, which is a bit resouce inefficient,