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

ERROR NaN found after 407 timestep

CL
chen ling, modified 6 Years ago.

ERROR NaN found after 407 timestep

Youngling Posts: 14 Join Date: 1/2/12 Recent Posts
Dear all,

When I am running a delft3d flow simulation (the boundary condition is the tidal difference), there is a error NaN found after 407 timesteps. I don't know what's the NaN mean,I have checked the open source, there are some program about NaN'S check, but I still don't understand what's the error is. Could someone give me some help to resolve this problem?

Thanks in advance!

Kind regards,

Chen Ling
Qinghua Ye, modified 6 Years ago.

RE: ERROR NaN found after 407 timestep

Jedi Council Member Posts: 612 Join Date: 3/2/11 Recent Posts
Dear Chen Ling,

NaN means Not A Number. There might be many reasons caused the NaN exceptions. Can you provide a bit more information? Or your model input to us for further investigation?

Regards,

Qinghua
CL
chen ling, modified 6 Years ago.

RE: ERROR NaN found after 407 timestep

Youngling Posts: 14 Join Date: 1/2/12 Recent Posts
Dear Qinghua,

Thank you so much to reply me.
The attachment is my model domain, and I specified two open boundaries for this coast, both of the boundary conditions are tidal levels, is it reasonable to specify boundary conditions like this? I did some local refinement on the small island, I am not sure that whether this is the reason.

Looking forward to you reply. Thanks again.

Regards,

Chen Ling
Qinghua Ye, modified 6 Years ago.

RE: ERROR NaN found after 407 timestep

Jedi Council Member Posts: 612 Join Date: 3/2/11 Recent Posts
Dear Chen ling,

There is a possibility that the boundary conditions are not well imposed. I still cannot see the cause yet.

The model domain looks fine. Local refinement should not matter as well. If current along the sea side is assumed to be parallel to the sea side boundary in your model, it is also possible to specify only 2 boundaries perpendicular to the coastline as a start. Using both boundaries as water level might be a problem, according to the textbooks.

You have the model results for 406 steps before the crash. Can you show some results from those steps?

Regards,

Qinghua
CL
chen ling, modified 6 Years ago.

RE: ERROR NaN found after 407 timestep

Youngling Posts: 14 Join Date: 1/2/12 Recent Posts
Dear Qinghua,

The attachment is the results. I am not sure how many open boundaries should be specified, just now I specified two open boundaries as that I have sent to you, some times I think three open boundaries should be given, the third one is towards sea side. Could you tell me that which is more reasonable?
Thank you very much.

Regards,

Chen Ling
Qinghua Ye, modified 6 Years ago.

RE: ERROR NaN found after 407 timestep

Jedi Council Member Posts: 612 Join Date: 3/2/11 Recent Posts
Dear Chen Ling,

The flow field looks fine with me. I cannot imagine what caused the problem.

Is the model a 3D, z-layer model? Or can you share the input of the model?

Regards,

Qinghua
CL
chen ling, modified 6 Years ago.

RE: ERROR NaN found after 407 timestep (Answer)

Youngling Posts: 14 Join Date: 1/2/12 Recent Posts
Dear Qinghua,

Thanks very much to give so many suggestions, these days I try to resolve the problem, luckily I am successful, just to decrease the time step very small.
Thanks again, and nice weekend!

Regards,

Chen ling
RC
Ana Rita Carrasco, modified 6 Years ago.

RE: ERROR NaN found after 407 timestep

Padawan Posts: 26 Join Date: 7/23/13 Recent Posts
Dear Qinghua,

I am having the same problem:
** WARNING Source and sink term sediment 1 reduced with factor 117.77 (m,n)=(1100,370), after 2345 timesteps.
*** WARNING Bed change exceeds 5.0 % of waterdepth after 2345 timesteps, location (m,n) = (594,2)
*** WARNING Bed change exceeds 5.0 % of waterdepth after 2345 timesteps, location (m,n) = (595,2)
*** WARNING Source and sink term sediment 1 reduced with factor 4173.23 (m,n)=(1,387), after 2346 timesteps.
*** WARNING Source and sink term sediment 1 reduced with factor 4985.81 (m,n)=(522,276), after 2346 timesteps.
*** WARNING Source and sink term sediment 1 reduced with factor 7043.34 (m,n)=(1,387), after 2346 timesteps.
*** WARNING Source and sink term sediment 1 reduced with factor 134.41 (m,n)=(1100,370), after 2346 timesteps.
*** WARNING Bed change exceeds 5.0 % of waterdepth after 2346 timesteps, location (m,n) = (595,2)
*** WARNING Bed change exceeds 5.0 % of waterdepth after 2346 timesteps, location (m,n) = (596,2)
*** WARNING Source and sink term sediment 1 reduced with factor 5149.07 (m,n)=(1,387), after 2347 timesteps.
*** WARNING Source and sink term sediment 1 reduced with factor 4899.92 (m,n)=(522,276), after 2347 timesteps.
*** WARNING Source and sink term sediment 1 reduced with factor 8681.80 (m,n)=(1,387), after 2347 timesteps.
*** WARNING Source and sink term sediment 1 reduced with factor 153.60 (m,n)=(1100,370), after 2347 timesteps.
*** WARNING Bed change exceeds 5.0 % of waterdepth after 2347 timesteps, location (m,n) = (594,2)
*** WARNING Source and sink term sediment 1 reduced with factor 6377.58 (m,n)=(1,387), after 2348 timesteps.
*** WARNING Source and sink term sediment 1 reduced with factor 4815.75 (m,n)=(522,276), after 2348 timesteps.
*** WARNING Bed change exceeds 5.0 % of waterdepth after 2348 timesteps, location (m,n) = (593,2)
*** WARNING Bed change exceeds 5.0 % of waterdepth after 2348 timesteps, location (m,n) = (594,2)
*** WARNING Source and sink term sediment 1 reduced with factor 10742.15 (m,n)=(1,387), after 2348 timesteps.
*** WARNING Source and sink term sediment 1 reduced with factor 175.73 (m,n)=(1100,370), after 2348 timesteps.
*** WARNING Bed change exceeds 5.0 % of waterdepth after 2348 timesteps, location (m,n) = (594,2)
*** WARNING Source and sink term sediment 1 reduced with factor 7930.70 (m,n)=(1,387), after 2349 timesteps.
*** WARNING Source and sink term sediment 1 reduced with factor 4733.28 (m,n)=(522,276), after 2349 timesteps.
*** WARNING Bed change exceeds 5.0 % of waterdepth after 2349 timesteps, location (m,n) = (592,2)
*** WARNING Bed change exceeds 5.0 % of waterdepth after 2349 timesteps, location (m,n) = (593,2)
*** WARNING Source and sink term sediment 1 reduced with factor 13343.79 (m,n)=(1,387), after 2349 timesteps.
*** WARNING Source and sink term sediment 1 reduced with factor 201.30 (m,n)=(1100,370), after 2349 timesteps.
*** WARNING Bed change exceeds 5.0 % of waterdepth after 2349 timesteps, location (m,n) = (595,2)
*** ERROR NaN found after 2350 timestep(s).
*** ERROR Flow exited abnormally


I am runing delft3d flow, 2D. How you manage to solve it Chen Ling?
Regards,

Rita
Qinghua Ye, modified 6 Years ago.

RE: ERROR NaN found after 407 timestep (Answer)

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

She reduced the time step to very small, if I understood correctly.

As I said above, there are too many reasons which can cause a NaN. You can try several things, such as, check the results before it crashes, reduce the time step, turn on the NaN check function(how to do this, pls refer to Adri's webminar), etc.

Hope this will help a bit?

Qinghua