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

flow simulations with "Closure error"

Dina Makarynska, modified 5 Years ago.

flow simulations with "Closure error"

Youngling Posts: 4 Join Date: 5/21/15 Recent Posts
Hi everybody,

I am trying to generate Flow (forced by astronomical constituents and time varying winds) and Wave (forced by a constant parameterised spectrum and same time varying winds) outputs to provide inputs for further suspended sediment/dredging operation WAQ runs. Along the way, I get the following warning/error messages, e.g.

WAQ input written at itime 60. Closure error: 0.306836E+01, 0.100000E+01( 9489): Total[m3], Max.Rel.(segment)
Maximum timestep: 16170.36 s in computational element: 9312

Would anybody be able to explain what it actually means and which part of input parameters needs attention to fix the problem?


Qinghua Ye, modified 5 Years ago.

RE: flow simulations with "Closure error" (Answer)

Jedi Council Member Posts: 612 Join Date: 3/2/11 Recent Posts
Hi Dina,

At the beginning and the end of each flow computation time step, the volume of the grid (waq segment) is compared and the small error is tracked and is written to a warning message. Usually this error is small and suppose to give you an rough idea about the mass balance. To decrease this value of the error, you might think about, such as, a smaller time step, smaller/better grid, less dry/wet change, etc.

However, usually you don't have to worry about this warning if the results of the model still look fine.