CfdOF mesh artifacts paraview

[Drdolittle]

Hello all,
I am new to this forum and have been reading through some of the posts to try to overcome an issue I am having.

I am currently using Freecad version 0.18 and the CfdOF workbench on a Windows 10 system. Visualisation of the model and resulting analyses are through Paraview 5.4.1 by clicking on the Paraview button in Freecad.

I am able to run CFD analyses, however the generated mesh always has artifacts in the internal structure of the model - I suspect these artifacts will be affecting the overall results of the CFD analysis. The model is imported as a Step file and prepared in Hexagon Designer.

Attached are some screenshots showing the issue.

Parameters used for mesh generation are:
Element Dimension: 3D
Mesh utility: cfMesh - note I used cfMesh for this example, however the same issue is seen with gmsh
Base element size: 0.5mm - note using smaller or larger values also results in artifacts

The first screenshot - "Internal Mesh Paraview - Extract Visible" shows the generated mesh in Paraview prior to running the CFD analysis. The artifacts are clearly seen as a diagonal boundary running between 2 chambers. You can also see in the Pipeline Browser the main model (OpenFoamReader1) and an ExtractCellsByRegion1.

First Screenshot

Internal Mesh Paraview - extract visible.JPG (175.14 KiB) Viewed 1535 times

The second screenshot - "Internal Mesh Paraview - Extract Not Visible" shows the generated mesh with the ExtractCellsByRegion1 turned off. This is how the model should look.

Second Screenshot

Internal Mesh Paraview - extract not visible.JPG (173.36 KiB) Viewed 1535 times

The final screenshot ("Multi chamber") shows the results of the CFD analysis opened in Paraview.
The resulting mesh shows blocky artifact areas which should not be in the analysis.

Final Screenshot

Multi chamber.JPG (29.02 KiB) Viewed 1535 times

Does anyone have an idea why this is happening, and how I can get clean mesh results with my analyses?

Your help is greatly appreciated.

Thanks
Denyse

[oliveroxtoby]

Hello all,
I am new to this forum and have been reading through some of the posts to try to overcome an issue I am having.

I am currently using Freecad version 0.18 and the CfdOF workbench on a Windows 10 system. Visualisation of the model and resulting analyses are through Paraview 5.4.1 by clicking on the Paraview button in Freecad.

I am able to run CFD analyses, however the generated mesh always has artifacts in the internal structure of the model - I suspect these artifacts will be affecting the overall results of the CFD analysis. The model is imported as a Step file and prepared in Hexagon Designer.

Attached are some screenshots showing the issue.

Parameters used for mesh generation are:
Element Dimension: 3D
Mesh utility: cfMesh - note I used cfMesh for this example, however the same issue is seen with gmsh
Base element size: 0.5mm - note using smaller or larger values also results in artifacts

The first screenshot - "Internal Mesh Paraview - Extract Visible" shows the generated mesh in Paraview prior to running the CFD analysis. The artifacts are clearly seen as a diagonal boundary running between 2 chambers. You can also see in the Pipeline Browser the main model (OpenFoamReader1) and an ExtractCellsByRegion1.


Internal Mesh Paraview - extract visible.JPG


The second screenshot - "Internal Mesh Paraview - Extract Not Visible" shows the generated mesh with the ExtractCellsByRegion1 turned off. This is how the model should look.

These aren't mesh artifacts but simply a second view on the data created as a convenience - a slice of cells through the model. This can be moved around by modifying the parameters to get different slices through your mesh, or turned off as you have done.

The final screenshot ("Multi chamber") shows the results of the CFD analysis opened in Paraview.
The resulting mesh shows blocky artifact areas which should not be in the analysis.


Multi chamber.JPG


Does anyone have an idea why this is happening, and how I can get clean mesh results with my analyses?

Your help is greatly appreciated.

Thanks
Denyse

I think this might be a paraview issue where inter-processor boundaries are visible, if you are viewing the decomposed case. Reconstructing the results with reconstructPar and viewing the reconstructed case should get rid of these.

[Drdolittle]

Thank you Oliveroxtoby for your quick reply. I will try reconstructpar to see if this clears it up.

I'm still new to CFD analysis in general, and the use of cfdOF specifically, (as well as paraview).

I see reconstructpar can be run from a command line for openfoam, however can it be run directly within Paraview?

If possible I'd like to stay gui based as that is one of the attractive features of the cfdOF workbench in Freecad over using openfoam directly.

Thanks again!
Denyse

[Drdolittle]

I've managed to answer my own question!

I see the option within Case Type which allows either the decomposed or reconstructed case.

Denyse