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: Coupled simulation yields unexpected outputs

Ruairi MacIver, modified 5 Years ago.

D3D-WAVE: Coupled simulation yields unexpected outputs

Padawan Posts: 45 Join Date: 5/1/13 Recent Posts
Comparing directional wave buoy observations with model outputs.

An uncoupled WAVE model (forced using wind and swell boundary conditions and with hydrodynamic properties set uniformly across the domain - zero current and no variation in water level) shows good agreement with observations (see figure PFOW_06c) over a month long simulation.

A three day simulation with a coupled WAVE-FLOW model (as above but with the hydrodynamic properties of water level and current (depth-averaged) only obtained from the FLOW model) shows the simulation over-predicting mean wave period and failing to resolve a short-lived increase in significant wave height (approx 12 hour duration) associated with a shifting (WNW to N) and strengthening wind (see figure FW_01 - simulation period is 3,4 & 5 May).

The observation point is in relatively deep water (50m) in a location of relatively small tidal flows (peak about 0.1m/s) with wind and swell seas approaching from the open sea (generally deeper water) in which current strengths are not significant.

Just wondering whether anyone has observed similar effects and might be able to shed some light on possible causes?

Ruairi MacIver, modified 5 Years ago.

RE: D3D-WAVE: Coupled simulation yields unexpected outputs (Answer)

Padawan Posts: 45 Join Date: 5/1/13 Recent Posts
To answer my own question ...

The differences were due to the fact that wind forcing of the wave model had been inadvertently turned off in the coupled simulation – the keywords WindGrowth & Quadruplets in the [Processes] section of the .mdw file had been set to false. So despite providing wind information – with the keywords MeteoFile in the [Domain] section – this was not applied during the simulation.

I had suspected it was a wind related issue but thought that wind forcing was being applied as I could plot the wind vectors in Quickplot. It seems the data specified by the MeteoFile keyword is included in the map output files regardless of whether it has any influence on the model.

I think the situation occurs as a result of my approach of preparing the .mdw file which was:
1) Use GUI to create initial .mdw. At this stage the keywords WindSpeed and WindDir {that appear in the [General] section} are zero by default and the keywords WindGrowth & Quadruplets {that appear in the [Processes] section} are not selectable in the GUI.
2) Directly edit the .mdw file to insert MeteoFile keywords in the [Domain] sections and to set the keywords WindGrowth & Quadruplets to true in the [Processes] section. In editing the file I either deleted the keywords WindSpeed and WindDir in the [General] section or left them at the default value of zero.

I think my confusion arose from re-editing the .mdw file using the GUI [for example, I tend to do this if changing simulation period as I am not confident changing the dates by direct edits of the simulation start/stop times in hours or minutes from the reference date, finding it easier to edit the dates in the GUI]. It appears that if the WindSpeed and/or WindDir keywords are omitted or WindSpeed is set to zero in the .mdw file then when opened in the GUI the WindGrowth & Quadruplets keywords are reset to false as the file is opened. There is a warning that this is occurring but it is easy to forget to subsequently directly edit the .mdw to return the keywords to true. This resetting of WindGrowth etc. doesn't happen if WindSpeed is set to some non-zero value.

I have it on good authority that specifying a MeteoFile keyword elsewhere in the .mdw file, in either the [General] section or [Domain] section, results in the WindSpeed keyword data being superseded by the MeteoFile keyword information. So it seems sensible to specify a non-zero WindSpeed if you are going to use MeteoFiles.

I hope this is clear.
Md Habib, modified 4 Years ago.

RE: D3D-WAVE: Coupled simulation yields unexpected outputs

Youngling Posts: 2 Join Date: 10/16/15 Recent Posts

I am trying run Delft3d wave standalone mode. I am using time varying spatially uniform wind, and wave boundary conditions with time and space varying. I have used TSeriesFile as keyword in additional parameter in GUI for specifying wave boundary condition. For wind data I have used keyword WindSpeed and WindDir at every Timepoint. The model is running fine. But the model output for wave parameter is showing no variation with time. Think the model is not reading the wind data. Could you please check my wave model setup.
RATHNASINHA JAYATHILAKA, modified 3 Years ago.

RE: D3D-WAVE: Coupled simulation yields unexpected outputs

Youngling Posts: 11 Join Date: 12/14/14 Recent Posts
Hi Mr. Ruairi,

Im working with a coupled WAVE-FLOW model (nesting). Once I have given both WindSpeed and WindDir in the BCW file the model worked properly.
But when i applied meteo files(xwind.wnd & ywind.wnd) into domain(wave grid) it gives following errors.

** Error : It is not recommended to use quadruplets
** Error : in combination with zero wind conditions.

Also i had similar problem when applying meteo files into nested D3D WAVE (stationary)..
Only with the single coarser domain it works perfectly but with nesting it gives following following error.

*** ERROR: Reading file "com-xxxx.dat" or "com-xxxx.def"

Can you pls help me in this regards.


Ps: .mdw and .wnd files attached