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! 

 

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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: 
/web/delft3dfm/forum
Post your questions, issues, suggestions, difficulties related to our Delft3D Flexible Mesh Suite on the new forum.

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** PLEASE TAG YOUR POST! **

  

 

Sub groups
D-Flow Flexible Mesh
DELWAQ
Cohesive sediments & muddy systems

 

Message Boards

Riemann condition - nan error

Fernando Barreto, modified 7 Years ago.

Riemann condition - nan error

Padawan Posts: 74 Join Date: 6/21/12 Recent Posts
Hi I'm trying to run a model using in the same boundary Water Level data and current time series. As I believe there is no way to directly use these data in Delft3D (are generated 25 m wl and the model blows) I decided to use the Riemann conditions. I generated boundary data using NESTHD2. However during the simulation, after 170 minutes of running the model accuses the existence of NAN, however there is no nan in the data. In another thread João Dias dos Santos also get a nan error when using Riemann.
Someone with experience in Riemann could help me?
The model is attached
Thanks,
Fernando
riemann nan

Attachments:

Adri Mourits, modified 7 Years ago.

RE: Riemann condition - nan error (Answer)

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

NaNs are filtered out by QuickPlot. And if an abort appears due to NaNs, no output is written anymore.

Are there any signals that the calculation becomes unstable (warnings in the tri-diag file, strange values in the output just before the abort)?

What happens with half the timestep you are using?

Regards,

Adri
Fernando Barreto, modified 7 Years ago.

RE: Riemann condition - nan error

Padawan Posts: 74 Join Date: 6/21/12 Recent Posts
Thanks for Reply Adri, I managed to solve the problem. It was related two things: the principal is the resolution between the coarser and refined grid (the second was very refined), and the segmentation of the open boundary (the riemann bc depends on depth). Just one more question, is Riemann the only way to enter water level and current in the same boundary and in the same time?

Thanks
Adri Mourits, modified 7 Years ago.

RE: Riemann condition - nan error (Answer)

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

Yes. See section "4.5.6 Boundaries". Nesting won't help you.

If both waterlevel and current prescription on your boundaries is that critical, you should enlarge your model and move the boundaries further away from your region of interest.

Regards,

Adri
MV
mercy varghese, modified 7 Years ago.

RE: Riemann condition - nan error

Youngling Posts: 17 Join Date: 8/6/13 Recent Posts
Hi Adri,

I'm very much new to Delft-3D. I'm trying to use Flow now to simulate storm surge

I know this post is pretty old...but I'm also encountering the NaN error.
I have land on the west and open boundaries on the north , south and east.
I'm using astronomical boundary conditions at the open boundaries
rectangular grids of 1.1km spacing and .5min time step
spatially varying wind field.

Any idea what may be the reason????

-mercy
nan error