Elmer Discussion Forum

I'm trying to simulate a fluid flow through a straight pipe (similar to the curved pipe thermal flow study). For this matter i've drawn my structure (straight pipeline + fluid body through it) and meshed it in Salome. When I tried to open it in Elmer I realized that the shared surface between the fluid and the pipe (where fluid and solid touch a.k.a no slip condition) is attributed entirely to the solid and my fluid has no "body".

Any idea how to solve this?

For the sake of clarity I've attached some photos.

"ElmerMesh" is the initial view of the system.
"FluidOnly" is the result when i Hide the body (pipeline)
"FluidExpectedOutcome" is my expected result when the body is hidden from view.

Thanks alot!

ElmerGUI has a condition when a boundary is shared between two bodies, that one body will not show in the GUI. This is because the GUI uses the boundaries to display the bodies. This is a graphical display issue only, and has no impact on the solution. It is caused by the boundary being attached to both bodies, but the GUI will only recognize the first one. The solver will work fine with this condition. However, if you want to resolve the graphical display in GUI you can manually edit the mesh.boundary file to remove the second (child) boundary association.

viewtopic.php?t=7692

I have not tested it but the graphical display would work if the boundary between the fluid and pipe switched the parent and child definition. The boundary between the two probably has the pipe as the parent and the fluid as the second. I don't know of a way to control which solid is the parent and which is the second, without manually editing the mesh.boundary file. However, as stated this has no impact on the solver, it is a GUI display anomaly only.

Another way to look at your model in ElmerGUI is to activate the volume mesh in addition to the surface mesh. Click on 'View' and you will see several list items, such as 'Surface mesh' which is active with a check mark by default, and 'Volume mesh' without a check mark by default. Click on 'Volume mesh' to activate the display of the 3D mesh.

Also, it almost always helps to post a sample file, such as a simple geometry file. A sample file will usually get advice that will best suits your particular case. You can post up to three file attachments at a time, up to a total of 1 MB in size.

Rich.

Thanks kevinarden and Rich for your useful input! I suspected it was indeed just a GUI issue but wanted to make sure it was the case. I'll make sure to include the file for the next time.

kevinarden wrote: ↑02 Dec 2022, 18:27 ElmerGUI has a condition when a boundary is shared between two bodies, that one body will not show in the GUI. This is because the GUI uses the boundaries to display the bodies. This is a graphical display issue only, and has no impact on the solution. It is caused by the boundary being attached to both bodies, but the GUI will only recognize the first one. The solver will work fine with this condition. However, if you want to resolve the graphical display in GUI you can manually edit the mesh.boundary file to remove the second (child) boundary association.

viewtopic.php?t=7692

kevinarden , thanks for the solution. I have a similar problem and I solved it. After I manually edited the mesh.boundary file and removed the second boundary association, everything is working fine.