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

Viewing pressure field results

SD
Steven Douglas, modified 6 Years ago.

Viewing pressure field results

Youngling Posts: 6 Join Date: 10/22/13 Recent Posts
Hello everyone,

I've been spending quite some time now trying to extract some results from a simulation I have successfully run. The simulation is a replica of a laboratory experiment in which a dam break wave impacts a square column. The objective of the experiment was to gain insight on the hydrodynamic forces exerted on the structural model by this turbulent hydraulic bore. The original plan was to view the resulting pressure field and to extract the calculated pressures in the grid cells adjacent to the column. I would then be able to obtain the resultant force by integrating these pressures over the inundated portion of the column.

However, I know that the pressures in each grid cell must be calculated when solving the governing equations, but I cannot seem to view the pressure field in quickplot. Does anyone know how I could possibly extract this information?

On another note unrelated to the original topic, I've been having some stability issues when using the Z-model. I find that the instabilities occur at low subgrid viscosity values. For example, when I select a constant horizontal eddy viscosity of 0.02 the model runs fine, but this viscosity seems to be too high for my grid size (in one simulation my structured grid is 2.5cmx2.5cm). At low viscosities (like the ones calculated from HLES) using sigma model everything runs fine. When I switch to Z-model it becomes unstable when the bore impacts the column. However, I would like to use the Z-model because the non-hydrostatic pressure solver should be used around the structure. Any thoughts/suggestions?

[EDIT] I should also mention that the momentum solver being used is 'flood'. I've noticed the instabilities vanish when switching to cyclic, but the nature of the problem requires the flood solver to be invoked. To my knowledge the tag version 3058 I am running contains the latest improvements to the Z-model.

Best regards,
Steven
Adri Mourits, modified 6 Years ago.

RE: Viewing pressure field results (Answer)

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

First you should check whether Delft3D-FLOW is an appropriate tool for this type of application. For detailed flows around structures, other packages may be more suitable, for example ComFLOW.

When doing a non-hydrodstatic (Z-layer) computation with Delft3D-FLOW the pressure is written to the map-file by default. I don't know what goes wrong in your case with QuickPlot. Alternatively, you can use the tool named "VSI" (part of the Delft3D-GUI). When you use that to open your map-file, the group named "map-series" should contain the element named "HYDPRES". Double-clicking this element will pop-up a second window in which you can choose to save the data to (ASCII-)file.

I'm not sure whether the flooding scheme works in the Z-layer model.

I'll forward this post to two colleagues. They will give additional information when available.

Regards,

Adri
SD
Steven Douglas, modified 6 Years ago.

RE: Viewing pressure field results

Youngling Posts: 6 Join Date: 10/22/13 Recent Posts
Hi Adri,

Before I implemented the non-hydrostatic pressure solver I was attempting to work out the instabilities that were occurring, so this explains why I wasn't able to view the pressure field. I'm beginning to think the perhaps the Z-model is not compatible with the flood scheme as well but I am trying to see what I can do.

Although it wouldn't help until I working out the instabilities, I get an error when I try to open the VSI. The error message that pops up doesn't exactly explain what went wrong so unfortunately I can't provide any additional information. It just tells me that it did not run successfully.

It would be great if your colleagues had any additional insight.

Thank you,
Steven
Adri Mourits, modified 6 Years ago.

RE: Viewing pressure field results (Answer)

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

Can you post a screenshot of the VSI error window?
Thanks.

QuickPlot is being improved to show the non-hydrostatic related parameters. I expect more info on this within a week.

You are right: The current flood scheme can not be used in combination with Z-layers. This is currently being investigated. I don't expect a solution for this within a month.

Regards,

Adri