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

 

Message Boards

Global to local

LA
Lara Ansanelli, modified 4 Years ago.

Global to local

Youngling Posts: 1 Join Date: 10/24/13 Recent Posts
Hi everyone,

I'm performing a model with Delft3D-Flow on Brazillian Northeast continental shelf and slope and I've found some problems.
I'm using Riemann conditions composed by Hycom results (u, v, water level, salinity and temperature) and TPXO harmonic. The model has 10 Z-coordinates levels (0.5 1 2 4 8 9.5 15 20 20 20 %). Looking at the bct and bcc files, I can see the hycom signal into all of the 10 levels. However, on second simulation time, the model suffers a "mixture" and the surface layer assumes the temperature, salinity and also the hydrodinamic pattern of the deeper layers. I've tryed to decrease the tstep to 0.1, but it has being the same.
The grid is regular and course (1500m x 1500). I'm using 1 m2/s for vertical eddy viscosity and vertical eddy difusity.
I will be greatfull to receive some ideas about how to block this "mixture'' process. Anyone is against using Delft-Flow to solve this meso-scale dynamics?

Thanks.
Bert Jagers, modified 4 Years ago.

RE: Global to local

Jedi Knight Posts: 201 Join Date: 12/22/10 Recent Posts
Hi Lara,

I'm not sure that I understand your problem correctly. You state:

Looking at the bct and bcc files, I can see the hycom signal into all of the 10 levels. However, on second simulation time, the model suffers a "mixture" and the surface layer assumes the temperature, salinity and also the hydrodinamic pattern of the deeper layers.


What do you mean by "second simulation time"? Do you mean the second time step of the simulation?

What do you mean by "suffers a 'mixture'"? Do you mean that there is too much mixing going on - in the vertical or in the horizontal, near the open boundaries or throughout the model?

Furthermore you state:

The model has 10 Z-coordinates levels (0.5 1 2 4 8 9.5 15 20 20 20 %).


What values did you specify in the bnd-file for the first layers: did you specify the near surface values or the near bed values? In a sigma-model Delft3D counts the layers from the surface to the bed (so, for layer 1 you need to provide the near surface values), but in a Z-layer model Delft3D counts the layers from the bed to the surface (so, for layer 1 you need to provide the near bed values). Note also that the first layer (0.5%) would be the lowest layer - I'm not sure that you actually intend to refine in the deep parts. So, the problems may be caused by a layer numbering issue.

Finally you state:

I'm using 1 m2/s for vertical eddy viscosity and vertical eddy difusity.


I think that these values are relatively high for the vertical coefficients. If you include k-eps model, I would recommend to just set these background vertical eddy viscosity and diffusivity values to 0 since the turbulence model should give the viscosity/diffusivity that you need.

Best regards,

Bert