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

Overestimation of tidal asymmetry

Menno Eelkema, modified 2 Years ago.

Overestimation of tidal asymmetry

Youngling Posts: 6 Join Date: 6/24/11 Recent Posts
Hi All,
I'm having a tenacious problem with a Delft3D-model of a well-mixed meso-tidal estuary. The model consistently overestimates the amount of flood asymmetry inside the estuary, quantified in the m4/m2-ratio of the vertical tide. The overestimation also shows in comparison between measured and modelled tidal discharge curves; the modelled flood period is shorter than the measured period, and has a higher maximum.

I've tried a lot of things to remedy it:
- double check the determination of tidal constituents (it checks out; both model and measurement span the exact same period for consideration)
- double check the bathymetry and geometry of the model (it checks out; M2-amplitudes, phases and tidal volumes are ok)
- vary the time step and spatial resolution (no effect)
- vary the bottom roughness over the domain (no effect on the asymmetry)

I'm running out of things to test and knobs to turn. Does anyone have any idea why a Delft3D-model might overestimate tidal asymmetry like this?

Thanks anyway,