## Simulation CFD

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# Hexagonal symmetry - unitary cell

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Hello

I am simulating a perforated sheet which has a traingular arrangement and hence hexagonal symmetry, as shown in the pic.

Now, since the holes of the perf are symmetric, it makes sense to use a unitary cell to simulate the perf. I have two questions.

1) Which unitary cell is most appropriate for this? The hexagonal one surrounding the single hole, or the rectangular one conering more holes?

2) Should I go for Symmetry or Periodic?

3) If periodic, how to number the hexagonal cell, (sides and pair numbers etc)

Regards

Omkar

Solved! Go to Solution.

# Re: Hexagonal symmetry - unitary cell

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If the purpose of this is to analyze a smaller section of a perforated plate to help characterize it and establish a distributed resistance equivalent, I would take the rectangular section you outlined as this will allow for you to see how the orifices interact with one another and if that would be something important to capture in the full model.

Periodic symmetry would not be used in either case that you outlined.

Periodic symmetry would be more towards modeling a single blade passage of a fan where flow exiting Periodic Pair 1 Side 1, would enter Pair 1 Side 2 with the same relative vector and magnitude. In your hexagonal section all sides are symmetric with adjacent hexagonal sections so Slip/Symm would be appropriate there

# Re: Hexagonal symmetry - unitary cell

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Thanks. I was referring to this paper:

Guo, B. Y., et al. "Numerical Modelling of the Gas Flow through Perforated Plates." *Chemical Engineering Research and Design* (2012).

The arrangement of holes on the perforated sheet in this paper is recrangular as against the triangular one in our design. Hence it made sense to take a unitary hexagonal cell, and assess the resistance coefficients etc. at different angle, without making it computationally expensive.

But I agree with you over more number of orifices being conisdered for their mutual interaction etc. It would be more meaningful that way. I believe the resistance coefficients would be close to each other for both cases.

Regards

OJ