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

Boundaries condition for tidal modelling

Anas Rahman, modified 6 Years ago.

Boundaries condition for tidal modelling

Youngling Posts: 21 Join Date: 10/4/13 Recent Posts
Hello everyone,

I am currently running tidal modelling, and there are a few things that I do not really understand

1. What is the difference between astronomic and harmonic forcing?

When I selected harmonic forcing for my model, the amplitude (current velocity) from my simulation results is extremely small compared with measured data

2. What is the difference between open boundaries type - water level and current?

When I first run my model, I chose water level for all of my boundaries (please refer the attached file for my model boundaries), and my result shows some underestimating /overestimating compared with measured data.

Then, from literature review, I noticed that most researcher will mix the type of boundaries condition. Thus, I change my boundary at the north and south to be water level, and set my boundaries at east and west to be current type, and it works well! Finally my simulation result is in agreement with measured data.

So the question is why can't I set all of my boundaries to be the same type? and which type is the best to be used for tidal modelling?

Thank you



Adri Mourits, modified 6 Years ago.

RE: Boundaries condition for tidal modelling

Yoda Posts: 1221 Join Date: 1/3/11 Recent Posts
Hi Anas,

Please have a look at our training courses.