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Seeting up Permeable Surfaces for use with FW-H Acoustics in CCM+

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Old   February 24, 2011, 06:37
Default Seeting up Permeable Surfaces for use with FW-H Acoustics in CCM+
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Matt Hollins
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Hi all,

I have found the CCM+ tutorial on using the FW-H analogy for aeroacoustics incomplete. It gives directions for setting up the impermeable surface (wall boundaries) but does not do so for the permeable surface - a very important feature when using FW-H!

I was hoping someone else might be able to point me in the right direction. When I try and set up a permeable surface I cannot select any parts to use as the surface - how do I go about this please?

I would also be grateful for any warnings of pitfalls I may encounter whilst conducting my analysis.

Thanks,
Matt
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Old   February 25, 2011, 13:22
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Vinicius Girardi
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You must create those surfaces inside the model as internal interaces and use them as permeable surfaces in the FW-H model.
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Old   February 28, 2011, 16:27
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Matt Hollins
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Thankyou for your reply Vinicius.

I have managed to do this now, however I am unsure what to set the boundary type to?

For example I have created a landing gear geometry. I have then created a sphere around this and set it up as an internal interface. The boundary still exists as a viscous wall though.

I want the boundary to not affect the fluid dynamics at all. Even setting it as a freestream condition would alter my results as flow features would not be able to propagate properly.

How do I counter this?

Thanks again for your help.
Matt
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Old   February 28, 2011, 16:30
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Matt Hollins
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Ahh, I think I may have been confused.

As the boundary does not have a part selected for it, then I do not think it exists and so is not a problem. I have selected the sphere for the internal interface though.

Is this correct?

Matt
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Old   February 28, 2011, 16:40
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Vinicius Girardi
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Thatīs correct. Once you create the interface between the boundaries they donīt have anymore their properties, but the interface ones...

So, for your permeable surface, select the internal interface youīve created.
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aeroacoustics, ccm+, fw-h, permeable, star-ccm+

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