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 xxxx timestep

karunakar kintada, modified 6 Years ago.

ERROR NaN found after xxxx timestep

Padawan Posts: 35 Join Date: 7/31/12 Recent Posts
Dear there,

i'm running flow (Hydrodynamics) module of the Delft 3d.
The model completes fine with tide boundary conditions.
but whenever i'm forcing wind on it, with *.spw files (Cyclones).
i'm getting the error: ERROR NaN found after xxxx time step.
It even occur for different domains. i was clue less.
i tried both linear and block interpolation schema in the dashboard.
Please let me know how this can be tackled.

Regards,
Karunakar
Adri Mourits, modified 6 Years ago.

RE: ERROR NaN found after xxxx timestep

Yoda Posts: 1224 Join Date: 1/3/11 Recent Posts
Hi Karunakar Kintada,

Do you also get NaNs when reducing the time step?

Do you get NaNs right at the start or somewhere during the simulation?

Regards,

Adri
karunakar kintada, modified 6 Years ago.

RE: ERROR NaN found after xxxx timestep

Padawan Posts: 35 Join Date: 7/31/12 Recent Posts
Hi adri,
Good to hear from you.
i've reduced the time step to a quarter. it still exists.
any other ways to manage this error??

i get this error in the middle of simulation, around 40 - 50% of simulation time.
Adri Mourits, modified 6 Years ago.

RE: ERROR NaN found after xxxx timestep

Yoda Posts: 1224 Join Date: 1/3/11 Recent Posts
Hi Karunakar,

First you have to find out whether the problems are caused by the model data or whether it is a bug in the source code. To exclude the first option:
Is there an error message/warning in the tri-diag file pointing to this problem? If you have a clue about when the problem appears, write to the map-file every timestep around this timepoint and investigate it.

Debugging the calculation is another option, but this normally is a long way. One easy thing to try is to switch on detailed NaN-checking: In source file "…\src\engines_gpl\flow2d3d\packages\manager\src\trisim.F90", activate 4 lines related to "raise exceptions" by removing the exclamation character (!) in front of these lines. Follow the instructions in the comments in this file. Then recompile the source code and use the resulting binary to run the simulation. I expect it will abort as soon as the first NaN appears, giving (hopefully) more info about what goes wrong.

Regards,

Adri
RC
Ana Rita Carrasco, modified 5 Years ago.

RE: ERROR NaN found after xxxx timestep

Padawan Posts: 26 Join Date: 7/23/13 Recent Posts
Hi Adri


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 can a solve it?
Regards,

Rita
Adri Mourits, modified 5 Years ago.

RE: ERROR NaN found after xxxx timestep (Answer)

Yoda Posts: 1224 Join Date: 1/3/11 Recent Posts
Hi Rita,

Check my posts above:
  • Reduce time step (check CFL condition, see manual)
  • Produce more output around the time point where the strange behaviour starts and investigate that
  • Switch on NaN check
  • Run it in a debugger


Regards,

Adri