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

Time series of current velocities for boundary condition (*.bct)

EA
Ed Atkin, modified 7 Years ago.

Time series of current velocities for boundary condition (*.bct)

Padawan Posts: 27 Join Date: 3/27/12 Recent Posts
I have a line of observation points spanning a natural harbour entrance, the model was driven with a water level time series. The objective was to extract tidally driven velocities through the harbour entrance, which was done successfully with observation points
The next stage is to use these tidally driven velocities in a finer resolution morphological model (The two models have not been officially nested and a curvilinear grid has not been used for specific reasons).

The relative, depth averaged velocity variables extractable from an observation point are vector, magnitude, angle and x/y or m/n components on their own. When it comes to constructing a time series of velocity data to put in to a *.bct file only two values for each time point can be stated: a value at point A and one at point B (start and end of boundary).

So my problem is representing the velocities extracted from my tidal flow model as a boundary condition comprehensively. If you use magnitude, then no direction is specified. If the x (m) component is used then the velocities in the y direction are not included (and vice versa).

Any ideas?
Qinghua Ye, modified 7 Years ago.

RE: Time series of current velocities for boundary condition (*.bct) (Answer)

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

Good question!

Standard Delft3D and other numerical modeling softwares cannot take the tangential velocity component into account as boundary conditions. We developed an extension of Delft3D with the tangential velocity boundary with the weakly reflective boundary condition (Riemann type boundary) and successfully applied in 2010. If you send me a email (qinghua.ye@deltares.nl), I can forward a conferece paper to you.

Unfortunately, the standardized function is not in the trunk yet. It is still in a side branch. You may be able to have a trial version, but no official support.

Regards,

Qinghua YE
EA
Ed Atkin, modified 7 Years ago.

RE: Time series of current velocities for boundary condition (*.bct)

Padawan Posts: 27 Join Date: 3/27/12 Recent Posts
Hi Qinghua,

Thanks for your reply. Ultimately the solution is to just nest. However I was trying to make some short cuts. I would like to read the conference paper please, but also if you have a trail version I would like to see if it works.

Kind regards,

Ed
FM
florian MONETTI, modified 7 Years ago.

RE: Time series of current velocities for boundary condition (*.bct)

Youngling Posts: 21 Join Date: 3/12/13 Recent Posts
Hi,

I would like to know if you found a solution to your problem.
I would like to input u,v values at my boundaries (ROMS model output) but as you said, only magnitude is posible (with current or Rieman boundaries).
Is there any way to do it?

Regards,

Florian
Ivana Bosnic, modified 6 Years ago.

RE: Time series of current velocities for boundary condition (*.bct)

Youngling Posts: 9 Join Date: 2/27/12 Recent Posts
Hi,

I also would like to know if you've found a solution to your problem. I have the same issue once I am trying to force my model using a time series of current velocities (magnitude and direction or u and v). Is there any recent development of the D3D model that allows this kind of forcing?

Thank you very much

Regards,

Ivana
Adri Mourits, modified 6 Years ago.

RE: Time series of current velocities for boundary condition (*.bct) (Answer)

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

It is still in a branch. Merging it the trunk is not planned yet.

Regards,

Adri
Felipe Arbeláez, modified 4 Years ago.

RE: Time series of current velocities for boundary condition (*.bct)

Youngling Posts: 2 Join Date: 3/13/15 Recent Posts
Hi everybody

I just have the same trouble which you have been talking about. I'd like to know if the newest version takes account tangencial and normal velocity components

Thanks
Adri Mourits, modified 4 Years ago.

RE: Time series of current velocities for boundary condition (*.bct) (Answer)

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

The bad news is that tangential boundaries are still in a branch only.

The good news is that it is based on a recent trunk version:
https://svn.oss.deltares.nl/repos/delft3d/branches/research/Deltares/20160110_tangential_boundary_conditions/

Regards,

Adri
VK
Vassilis Kolovoyiannis, modified 4 Years ago.

RE: Time series of current velocities for boundary condition (*.bct)

Youngling Posts: 1 Join Date: 3/18/14 Recent Posts
Dear all,

I have velocity data extracted from a larger-scale model (u and v components, in the x-east and y-north direction respectively, ROMS model) that I intent to use as boundary data in a finer scale DELFT3D implementation. The open boundaries of this nested model are curved, not following the orthogonal linear grid of the larger scale model.

In cases like this and the ones shown in Figure 1 (the grids come from the Deltares report by Ye and Morelissen, 2011, entitled ‘Implementation and validation of tangential boundary conditions in Delft3D-FLOW’), where the nested model boundaries are at angles with the larger model grid, how is the perpendicular-to-the-open-boundary (normal) component of the velocity actually computed?

Does one have to calculate the projected velocity component (red vector in the attached Figure 2) onto the normal line (blue) at all boundary points in order to get the ‘normal’ boundary velocity and create a .bct file from this data set?

Thank you in advance for your time.

Vassilis
Qinghua Ye, modified 4 Years ago.

RE: Time series of current velocities for boundary condition (*.bct)

Jedi Council Member Posts: 612 Join Date: 3/2/11 Recent Posts
hi Vassilis,

Indeed your computation is right. You may use the projected velocity in the normal direction. As we described in the paper, the velocity information along the boundary would be lost. Thus we introduced other alternatives in the paper.

I hope this is a bit helpful,

Qinghua YE