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

Change geometry of a local weir + instabilities due initial conditions?

CM
Constanzo Marullo, modified 5 Years ago.

Change geometry of a local weir + instabilities due initial conditions?

Youngling Posts: 10 Join Date: 1/21/13 Recent Posts
Hi all,
I'm currently developing a model for an overtopping dam break scenario using Delft3D and I've got several doubts about the right steps to follow.

I want to simulate the flow through the breach as a broad-crested weir. Research about the shape and development characteristics suggests using a trapezoidal section for it. However, I've been reading Delft3D-FLOW manual and there's no information about a possibility to set a shape for local weirs (Special features on Delft3D Chapter, Page 501 only explains how to input crest height as geometry information).

If it's not possible to change the geometry, I was thinking of making a channel with bathymetry information in order to maintain the shape and consider local head loss increasing bed roughness in the area.


On the other hand, I want to take into account the influence of the breach opening process in the resulting discharge rate. My plan consists in running the model a couple of times, change weir (or channel) section and use the results in the reservoir as initial conditions for the next run. Even though I thought it was a good strategy, my project advisor told me that it may yield to some instabilities due to level and velocity incongruities. Has anyone used something similar? I haven't tried this yet.

I'd rather not use RTC Tools.

Any suggestion or comment would be really appreciated.
CM
Constanzo Marullo, modified 5 Years ago.

RE: Change geometry of a local weir + instabilities due initial conditions?

Youngling Posts: 10 Join Date: 1/21/13 Recent Posts
Hello everybody,

I've been thinking about the weir's geometry and the fact is that i can't really understand this statement (extracted from Delft3D-FLOW manual)

"A local weir is modelled as a sub-grid phenomenon, i.e. its dimensions are (assumed to be) much smaller than the grid size and only its overall influence on the flow is taken into account. This overall influence is modelled by the energy losses due to the weir."

If I have a 50m x 50m grid cell and I set a weir on it, does this mean that it won't have an equivalent geometry of cell's dimension as width (50m) and crest height?
Adri Mourits, modified 5 Years ago.

RE: Change geometry of a local weir + instabilities due initial conditions?

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

No, you can specify the correct sizes of the weir. The manual tries to say that Delft3D-FLOW is not designed to model detailed flows around structures. Other packages may be more suitable, for example ComFLOW.

May be this thread will help.

Regards,

Adri