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periodic boundary condition

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Old   October 11, 2014, 03:40
Question periodic boundary condition
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adnan aziz
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hi all

i am in a bit of a fix here. i need to do analysis in fluent of a 1000mm internally grooved tube with thermal condition in ansys fluent.

can somebody please answer the following questions:

1. can internally helical grooved tubes be structurally meshed? if yes how?

2. i have already meshed it unstructurally. the trouble is when i run it in fluent, it consumes a lot of memory. i have 32 GB RAM and still the fluent is taking 6-7 hours per iteration. is there another way to run the calculation? somebody told me to reduce the length of the tube to 10 mm and apply periodic boundary condition for 1000mm, i dont understand what it is? can somebody explain the way to do it?

urgent help required please, very desperate
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Old   October 12, 2014, 05:55
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Cees Haringa
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Hello Adnan,

Yes, it should be possible to apply a structured mesh in this geometry. In the ANSYS meshing tutorials and examples (which you can find on the ansys costumer portal) different ways for meshing a pipe are outlined.

In order to apply a structural mesh, you may have to modify the geometry a bit - for one, separate the grooves from the tube such that the tube is smooth (that's what I would do for ansys meshing - if you use ICEM there may be different options, but I have no experience there).

From your picture, it seems the grooves are spiralling around the tube. This complicates the geometry - is this spiralling necesarry for your calculations, or could you use straight axial grooves? That would be very benificial for structured meshing - and necesarry to use cyclic boundary conditions.

When using cyclic boundary conditions, you assume there is a rotational symmetry, in this case around the axis of the tube. That means you don't need to model the entire tube - only a section with one groove - which would decrease your computational cost significantly.

Good luck!
Cees
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