# Mesh strategy for 5 bodies geometry to be used in FLUENT

Member Posts: 2
edited March 24

Dear all,

I am trying to do the mesh of a water solar collector, which is composed of 5 materials: Fluid, Solid (representing the thickness of the tubes and collectors), absorber, glass and a cavity (representing air). As I am interested in modelling heat transfer and fluid flow among all bodies in Fluent, after being reading the guides I understood that I need a conformal mesh. Therefore, in Desing Modeller I create the 5 bodies and I generate a New part putting inside it the 5 bodies, see attached file.

I was doing the mesh tutorials and workshops, but I am a bit lost and I do not what type of strategy to follow for doing a mesh with the smallest number of nodes, I am completely lost and I do not know which strategy to follow. The tutorials available are focus on single bodies. Any recommendation on the strategy to follow for this case?

The geometry is shown on attached file

Naiara

• Posts: 3,298Forum Coordinator

If bodies are sweepable, please use hex mesh.

Ansys Meshing Sizing:

Regards,

Keyur

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• Posts: 5Member

Dear Keyur,

Attached the images

Thank you

• Posts: 11,378Member

I recommend you slice all bodies using 2 planes parallel to YZ. One plane will be 25 mm along +X from the top internal solid wall. Another plane will be 25 mm along -X from the bend at the bottom of the tube.

That will create a center block that has perfectly sweepable solids. That will allow you to create a low node count mesh because you can make the element size large in the X direction while it can be small in the Y and Z directions to capture the boundary layers in the water and air on the tube surfaces.

The top and bottom blocks are a much smaller volume and can be meshed with tet elements.

In all three blocks, you want inflation layers in the air on the tube OD and in the water on the tube ID.

• Posts: 5Member

Dear Peteroznewman,

Do you mean to do slice through these planes, for example?

Slicing all bodies through those planes here is the results:

Due to that, the original 5 bodies (each one corresponds to a different material) are now divided and I have so many bodies inside the part, look below:

For example, the absorber material is now divided in 3 bodies. As the three bodies form the same material (the absorber) inside Design Modeler, I need to share topology of the three bodies which form absorber? If this is right, the same procedure should be follow for each initial body that have being divided in many parts? That is share topology among the bodies that form water; share topology among the bodies that form tubes thickness, etc.

As heat transfer is going to be model among the 5 different materials they should be inside the same part in Design Modeler. But now if I slice those materials they will be decomposed, so I need to share topology among the divisions of the same material to form a single continues body for each material?

Kind regards,

Naiara.

• Posts: 11,378Member

Naiara @bgproann

Slice on planes represented by the red lines. That way, the middle section is what ANSYS calls "sweepable" bodies. That allows you to have fewer nodes and elements in that middle section that it would if you did not do the slicing. Yes, it makes three times more bodies than you had, and Share Topology will allow the mesh to be congruent across these new faces as well as all the existing faces.

• Posts: 5Member

Dear Peteroznewman,

I was able to do the mesh on the five bodies (water, tubes thicknes, Cavity=air, absorber and glass), in the next images you can have a look to the results.

The number of nodes is 4,9 millions, too much for doing Fluent modelling later.

In the sweep method I select the next options for water and tubes sweep:

And in the sweep method for glass, absorber and cavity (air) the next features:

And in general mesh size option I have:

If I try to increase Sweep element size in tubes and water to 6 mm, for example, I get the following error: "patch-conforming tetrahedron mesh failed because of an edge intersection". Any recommendation of what can I do to reduce the number of nodes?