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! 

 

=======================================================
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.

=======================================================

** PLEASE TAG YOUR POST! **

 

 

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

 


Message Boards

bed roughness file

XL
Xiujuan Liu, modified 5 Years ago.

bed roughness file

Youngling Posts: 13 Join Date: 10/15/13 Recent Posts
Hi all,

I tried to use the formula Manning coefficient=0.015+0.01/depth to obtain a space varying bed roughness file. I did it through quickin. The calculated Manning coefficient at the points with negative water depth is negative or less than 0.015. If I run the model with this roughness file, it can be run but will stop very soon with the error ' zero or negative value found for bed stress coefficient'. If I change the Manning coefficient whose value is less than 0.015 into 0.08 and then run the model, this model can not be run with the error 'Read error from file *.rgh'.

Under these two situations, I don't make any change at the points whose Manning coefficient is -999. In addition, if I set the Manning coefficient to a uniform value 0.02, the model can be run normally.

I attach the two roughness files. The first file was obtained using quickin without any change and the second was also obtained using quickin but with some change described above.

Any comments will be highly appreciated.
AA
Anonymous Anonymous, modified 5 Years ago.

RE: bed roughness file

Padawan Posts: 75 Join Date: 7/30/20 Recent Posts
First, Manning's roughness should not go to negative.

Second, did you include roughness for both u- and v- directions?
XL
Xiujuan Liu, modified 5 Years ago.

RE: bed roughness file

Youngling Posts: 13 Join Date: 10/15/13 Recent Posts
Thank you for your reminder.

Could you please tell me how to deal with the points with negative water depth since Manning's roughness should not go to negative?

Yes, I included roughness for both u- and v- directions.
AA
Anonymous Anonymous, modified 5 Years ago.

RE: bed roughness file

Padawan Posts: 75 Join Date: 7/30/20 Recent Posts
Hi,

Do you use this mentioned formula:
Manning coefficient=0.015+0.01/depth

I am not aware of this formula. Is it from some literature (please let me know if it is)? Probably you can take a look at Manning's coefficient in other models for the same area.

Regards,
Ke
Qinghua Ye, modified 5 Years ago.

RE: bed roughness file

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

I am not sure about the formula you used as well.

In the .rgh file, if you replace all the negative value to 0.0, there would be no error.

Hope this would be helpful.

Qinghua
XL
Xiujuan Liu, modified 5 Years ago.

RE: bed roughness file

Youngling Posts: 13 Join Date: 10/15/13 Recent Posts
Hi Qinghua,

I tried to replace all negative values with 0, but there still exists such error: *** ERROR Read error from file: test.rgh
*** ERROR Flow exited abnormally.

Any other suggestion?

Thank you very much.

Best regards, Xiujuan
Qinghua Ye, modified 5 Years ago.

RE: bed roughness file

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

I need to see the input files and the rgh file again. Can you post it or send them to me?

Regards,

Qinghua
XL
Xiujuan Liu, modified 5 Years ago.

RE: bed roughness file

Youngling Posts: 13 Join Date: 10/15/13 Recent Posts
Hi Ke,

Yes, I use this formula to calculate the Manning coefficient.

Yes, it is from a paper published in Marine Geology. The detailed info: Xing et al., 2012, Tidal hydrodynamics and fine-grained sediment transport on the radial sand ridge system in the southern Yellow Sea. Marine Geology, 291-294, 192-210.

I will take a look at other formula about Manning coefficient. Thank you for your suggestion.

Regards, Xiujuan



K Liu:
Hi,

Do you use this mentioned formula:
Manning coefficient=0.015+0.01/depth

I am not aware of this formula. Is it from some literature (please let me know if it is)? Probably you can take a look at Manning's coefficient in other models for the same area.

Regards,
Ke