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CFD(Hypermesh) Hex-Core_BL-Hex

Hello
I am using CFD(Hypermesh) and i want to mesh a simply pipe geometry. Afterwards i want to export it to OpenFOAM. To reduce the number of elements as many as possible I want to combine a hexaeder Boundary layer and a hex-core mesh as shown in the youtube-video: http://www.youtube.com/watch?v=tn_RfdyUwH4
My problem is that hypermesh doesnt generate pyramids for the transition zone between boundary layer hexaeder to exterior tetraeder mesh, when using hex core meshing. Please Help me.
Thank you

Tobias

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Rahul_P1

Tobias,

You can first generate the BL and the tetramesh using CFD tetramesh panel, here you will need to use one of the pyramid options in the BL hexa transition mode of the BL Parameters.
CFD Tetramesh > BL parameters > BL hexa transition mode > smooth pyramid for instance.

You can delete all the tetras alone so that you will have the BL and pyramids from the BL left.generate face elements on the exposed inner faces of the pyramid elements, i.e. faces that are not attached to any other element.lets call this faces_pyra_bl

You can then generate a hex core using only the surface elements. while generating hex core the options should exclude generate exterior tetrahedral mesh and boundary layer, this will create only the hex core, it will also automatically create pyramids on the hex, and faces of these pyramids in the faces_pyra_hex collector.

Create a closed surface mesh volume between the faces_pyra_hex and the faces_pyra_bl. Generate tetras to fill this closed volume thus completing your model.

Rahul

Rahul_P1

Rahul
thank you, for your help. I achieved the point where I have to create a closed surface mesh volume between the pyramid-faces. Could you explain me how to create this mesh?

Tobias

Rahul_P1

Tobias,

Here since you need a tetramesh you will be using the tetramesh panel that will require a closed volume to generate the mesh.

In my example model I use my inlet and outlet to close my pyramid faces and create a closed volume, then I use tetramesh to fill this space with tetras.

I use fixed input surface mesh so as to ensure the tetramesh does not change the pyramid faces mesh at all.

see HM-3200: Tetrameshing and tetramesh panel help documentation for help on using the tetramesh panel.

Rahul_P1

Tobias,

Depending on your model you could also use CFD tetramesh panel to create both the boundary layer and the tetramesh for the volume,

In this panel you can use the sub panel tetramesh parameters you can control the growth rate of the tetras hence controling the number of elements in the core of your model, this is an alternative route for you to approach your analysis which will also decrease the number of elements.

Rahul_P1

Did you create a solid by surfaces to get the closed volume? When yes, how did you create the surfaces?
Or did you use Volume_Mesh/Tetra_mesh?

Thx for your help, and a nice weekend!!

Rahul_P1

Tobias,

In my model I created surfaces from the solid, I deleted the solid and did not check the bounding surfaces when deleting them, thus deleting only the solid and leaving the surfaces.

I then mesh the surfaces and then use CFD tetramesh.

Rahul_P1

It worked. After building the core I used CFD TetraMesh to Mesh the Boundary Layer and the Transition Zone. To get the connection between the core and the Transition Zone i defined the Faces from the Core under 'w/o boundary Layer'.

Thx for your help!