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

Morphological updating methods in D3D (online and tidally-averaged)

Zeng Zhou, modified 8 Years ago.

Morphological updating methods in D3D (online and tidally-averaged)

Youngling Posts: 1 Join Date: 12/11/11 Recent Posts
Hi everybody,

I am currently doing some long-term simulations using D3D. To bridge the time-scale difference of hydrodynamic and morphological change, the current D3D model adopts the so-called online method which computes the hydrodynamics, sediment transport and morphology change at the same hydrodynamic time step and the obtained bed level change is mutiplied with a Morpho Accelaration Factor to feed back to the next time step.

For research purpose, I am interested in the previous tidally-averaged method that was adopted by D3D several years ago. This method assumes that the bed level does not change within one tide and the associated sediment flux during the hydrodynamic time step is summed up during that tide to evaluate the bed level change. Once the bed level change reaches a threshold, the bathymetry is updated and adopted for the subsequent calculation of hydrodynamics (next time steps), etc.

I am wondering if it is possible to switch to the tidally-averaged method easily using the current D3D model. If anybody has some opinions or experience, could you please let me know. Thank you in advance.

Dano Roelvink, modified 8 Years ago.

RE: Morphological updating methods in D3D (online and tidally-averaged) (Answer)

Youngling Posts: 2 Join Date: 3/23/11 Recent Posts
Dear Zeng,

The tide-averaging option is not implemented in the present Delft3D-version but it is not difficult to tinker such a version in a combination between Delft3D and Matlab. I did something like that in my 2006 paper in Coastal Engineering. The simplest is as follows:

0. prepare a Delft3D run with an initial spin-up period and one tidal cycle of morphological updating with morfac=1
1. run Delft3D
2. extract bottom changes after one tidal cycle, e.g. using vs_get
3. multiply bottom changes by factor (morph. timestep/tidal period)
4. update bathymetry accordingly
5. write new dep file
6. back to 1

You can carry out these steps from a Matlab script.

Alternatively, you could extract the total transports from the trim file and grid quantities from the com-file and write your own updating scheme in Matlab.

In summary, it is doable with a little effort, and at least you can leave the wave, flow and transport simulations to Delft3D.

Good luck,

Dano Roelvink