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

Solving convection diffusion equations

U
Leyang Liu, modified 4 Years ago.

Solving convection diffusion equations

Dear Sir/Madam,

I’m using Delft-3D to build a model in order to verify the theoretical solutions to the convection diffusion equations. But I always get the numerical results that obviously diffuse faster than theoretical results.

The results and details of the two cases I build can be seen in the attachment.

Could anyone please help me to find possible causes? Or could you make some recommendations of people who might help me?

Many thanks and your valuable aid is very much appreciated.

Best,

Leyang Liu
U
Leyang Liu, modified 4 Years ago.

RE: Solving convection diffusion equations

Hi, everyone!

About my last thread stating that the numerical results obviously diffuse faster than theoretical results when I try to solve convection diffusion equations, I have new discoveries!

I find some lines of the source code of Delft-3D use the diffusivity coefficient given in the GUI by making them divided by 0.7 at first. For instance, ‘difco = 0.5*(dicuv(nm, kll) + dicuv(nmu, krr))/0.7’.

So I speculate that the diffusivity coefficients given in the GUI are 0.7 times those actually used in calculation. Then I apply this in my test cases and I get perfect-matching results as shown in the listed figure.

After that, I find some explanations about diffusivity coefficients and Prandtl-Schmidt number in Delft’s manual (I make screenshots and show them in the same figure).

I’m not sure about the validity of my speculations, and I don’t know if I find the right cause, either. So can anyone give some theoretical explanations about this to me? Or point out my wrong understandings? Anything from you would be appreciated very much.

Best wishes,

Leyang Liu
MJ
Michel Jeuken, modified 4 Years ago.

Move thread

Jedi Knight Posts: 154 Join Date: 1/21/13 Recent Posts
Dear Leyang Liu,

Your question does not concern Delwaq (the dedicated water quality module), but substance transport in the FLOW module. There I move you thread to the general forum.

Michel
U
ZULHAFIZAL OTHMAN, modified 3 Years ago.

RE: Solving convection diffusion equations

Dear Leyang Liu,

May I have your email? Because I'm doing quite same with you which is convection diffusion equation.. Maybe we can have further discussion.. Or you may email direct to me (zulhafizal445@pahang.uitm.edu.my)

Thank you..

Regards,
ZULHAFIZAL
U
Leyang Liu, modified 2 Years ago.

RE: Solving convection diffusion equations

Dear ZULHAFIZAL,

Thank you for your posting, and I'm very sorry for my late reply.

Unfortunately, I have finished that project a long time ago and haven't been using Delft-3D for a very long time. So I may not be the best person to answer your question if this is still troubling you.

However, I've already received an email from Deltares which told me the research staff have already found this inconsistency within the software. So I think maybe you could send emails to them to check and pursue explanations.

Hope this helps!

Best wishes,

Leyang