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

D3D-WAVE: Quirks when using SpectrumSpec = from file

Ruairi MacIver, modified 6 Years ago.

D3D-WAVE: Quirks when using SpectrumSpec = from file

Padawan Posts: 45 Join Date: 5/1/13 Recent Posts
The following is an observation of a quirk when applying time varying wave boundary conditions using the TPAR file approach in the present version of Delft3D-WAVE. The TPAR file approach requires the keyword 'SpectrumSpec = from file'. The quirk can be summarized in the following pseudo-code:

if 'SpectrumSpec = from file' then
SpShapeType, PeriodType, DirSpreadType will be set to jonswap (3.3), peak, power
elseif 'SpectrumSpec = parametric' then
SpShapeType, PeriodType, DirSpreadType can be set, either manually or through GUI

This is despite section A2.8.4 of the Delft3D-WAVE manual suggesting that PeriodType [peak or mean] and DirSpreadType [power or degrees] can be set within the GUI.

I've passed this by folk at Deltares who have confirmed this quirk. Hope this helps someone.

Longer Description
Inspection of the intermediate SWAN input files indicates that when the boundary condition parameters are contained in a TPAR file they are passed to SWAN as if the period and directional spread values in the TPAR file represent a peak period and a cosine power. It also seems the spectral shape is presumed to be JONSWAP with a peak enhancement factor value of 3.3.

Creating the MDW file using the GUI and indicating that the boundary condition will be provided via a TPAR file (at the Specification of Spectra section using the ‘from file’ button) results in the following keyword structure in the MDW file.
Name = b_name
Definition = orientation [for example]
Orientation = west [for example]
SpectrumSpec = from file
Spectrum = TPAR06.bnd

The information that appears in the subsequent SWAN input file is
BOUN SIDE b_name CCW CON FILE 'TPAR06.bnd' 1

Manually editing the MDW file to include other keywords (e.g. SpShapeType, PeriodType, or DirSpreadType) has no influence on the content of the SWAN input file. The manually entered keywords appear to be ignored in the creation of the *.swn file.
Marjorie Turiano, modified 3 Years ago.

RE: D3D-WAVE: Quirks when using SpectrumSpec = from file

Youngling Posts: 19 Join Date: 1/22/16 Recent Posts

This is still the situation in the version (SWAN Deltares Version Number 40.72ABCDE) that I am using. How do you suggest to work around this? My input TPAR uses mean period and spread in degrees.