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[ICEM] Meshing of a pipe with a helix structure help needed

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Old   November 30, 2017, 08:10
Default Meshing of a pipe with a helix structure help needed
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Thijs
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Hello people,

For my master thesis I study fully-developed flows in pipes with a helix structure. The CFD analysis will be done in openFoam and the meshing the geometry using ICEM CFD 18.2 . The flow-domain (geometry) is first drawn using Solidwork and import in ICEM CFD using import model function.

My first thought was that I have to create a structured grid using hexahedral elements. So I used in ICEM the create block utility and associated edges to curves at both inlet and outlet. The following step I did was using ogrid and then pre-mesh. This is bassically the way to go for creating a structured grid for a pipe, but my mesh fails in accurately capturing the helix geometry.

My question is: is a structured hexahedral mesh possible? Or should I use something else. Or should I consider using an unstructured mesh?

Kind regards,

Thijs











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Old   November 30, 2017, 13:29
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kad
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Your blocking does not respect the geometry of the helix at all. This why you get bad elements there. You have to account for the helix geometry by doing further splits associations and so on. I guess it would be rather painful to do a full 3D blocking for the whole geometry.

My idea is to try this one with the extrusion tool. So you begin with 2D blocking or mesh a e.g. the inlet and afterwards extrude with combined rotation and translation, which is possible in ICEM. Your extrusion parameters then have to fit your geometric parameters of the helix.

I took two quick shots at it, see attachments. First one is to start with a real easy blocking for the upper surface. After converting to unstructured mesh, the mesh is smoothed with orthogonality tool to improve the mesh in the small "bump region". Another strategy would be to improve the blocking itself. This is followed directly by the extrusion.

The second try starts with a unstructured quad dominant mesh. You can use the "curve mesh setup" parameters to create some kind of boundary layers. The rest is exactly the same procedure.
Attached Images
File Type: jpg helix2d.jpg (112.2 KB, 23 views)
File Type: jpg helix3d_1.jpg (121.4 KB, 23 views)
File Type: jpg helix3d_2.jpg (123.6 KB, 24 views)
File Type: jpg helix_unstr1.jpg (115.1 KB, 22 views)
File Type: jpg helix_unstr2.jpg (124.2 KB, 24 views)
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Old   November 30, 2017, 17:27
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Quote:
Originally Posted by kad View Post
Your blocking does not respect the geometry of the helix at all. This why you get bad elements there. You have to account for the helix geometry by doing further splits associations and so on. I guess it would be rather painful to do a full 3D blocking for the whole geometry.

My idea is to try this one with the extrusion tool. So you begin with 2D blocking or mesh a e.g. the inlet and afterwards extrude with combined rotation and translation, which is possible in ICEM. Your extrusion parameters then have to fit your geometric parameters of the helix.

I took two quick shots at it, see attachments. First one is to start with a real easy blocking for the upper surface. After converting to unstructured mesh, the mesh is smoothed with orthogonality tool to improve the mesh in the small "bump region". Another strategy would be to improve the blocking itself. This is followed directly by the extrusion.

The second try starts with a unstructured quad dominant mesh. You can use the "curve mesh setup" parameters to create some kind of boundary layers. The rest is exactly the same procedure.
Hi Kad,

Thank you for you tips and your effort for spending some time figuring out my problem. I will try this the first thing in the morning and I will report back with my experience.

Kind regards,

Thijs
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