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

Mass Balance Error?

Gyan Basyal, modified 6 Years ago.

Mass Balance Error?

Youngling Posts: 7 Join Date: 5/16/12 Recent Posts
Hello everyone,

I have been comparing net volume of sediment deposited in a closed reservoir to total volume of input sediment but they don't match up.

In order to calculate the former, I use cum. erosion/sedimentation data. Each data point multiplied by grid area (say 50 m by 50 m) gives net eroded or deposited volume at a point. Summing up positive values gives deposited volume and summing up negative values gives eroded volume. Adding them both gives net deposited volume assuming that you have sediment entering in to the system. Solid volume of the bed is then calculated by multiplying bulk bed volume with dry density of the sediment.

I am using a morphological factor, so I multiply input sediment with this factor to calculate total sediment inputted into the system during the period assuming eventually all sediment will deposit (which is true in my model). Comparing the solid volume of sediment in bed to inputted sediment, I find the former is 65-90 % of the latter. There is indeed some sediment in suspension not accounted for in the bed volume calculation but I don't think it should make such significant difference.

Is there anything wrong did I do in this comparison, or is it something you have experienced too? I would like to add that I have this issue when I have "sand" in the system. I have checked that the sediment isn't escaping the system and also tried smaller value of morphological factor. Introducing clay into the system, however, the comparison has matched up well. I am using default Van Rijn formulation for sediment transport and 3246 tag version.