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

Sediment Volume

Christopher Esposito, modified 7 Years ago.

Sediment Volume

Padawan Posts: 35 Join Date: 10/16/12 Recent Posts
I am having a problem tracking the volume of sediment that I put into my model. There are three sediment fractions in my model, but I will just talk about the silt for the moment.

My input concentration of silt is 0.0667 kg/m^3.
The water discharge at my entrance is 1500 m^3/s.
The dry density of silt is 500 kg/m^3_bed.

I would expect that the instantaneous transport of silt, measured at a cross section at the entrance, could be calculated as follows:

0.0667(kg/m^3)*1500(m^3/s)/500(kg/m^3_bed)=0.2 m^3_bed/s

But when I plot the instantaneous total transport of the silt fraction in Quickplot, I see that the number holds steady at 0.037 m^3/s. I get the same answer if I read the files in with matlab and add the suspended and the bed components of the silt fraction, or if I estimate the number from the plot from the map file.

I would like to think of that instantaneous total transport number as the total volume(in the bed) of sediment that I have input to the model. Am I thinking about this calculation incorrectly?
Richard Measures, modified 7 Years ago.

RE: Sediment Volume

Jedi Knight Posts: 178 Join Date: 3/23/11 Recent Posts
Hi Christopher,

I think the volumetric transport rate is output in terms of solid rock volume. If you do the same calculation but replace your dry bed density of 500 kg/m^3 with the density of the solid material the silt is made from (RhoSol in the *.sed input file) I think you'll get the correct answer. I tried this assuming RhoSol = 2650 kg/m^3 (the default value) and got:

0.0667(kg/m^3)*1500(m^3/s)/2650(kg/m^3) = 0.037

Hope that helps,

Christopher Esposito, modified 7 Years ago.

RE: Sediment Volume

Padawan Posts: 35 Join Date: 10/16/12 Recent Posts
Oh, of course...Thanks Richard...That solved the problem for the cohesive fractions. My sand boundary was also a problem, but it looks like I had EqmBc in my morphology file set incorrectly. I assume that once I set that to false, my numbers will work out.