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Old   September 20, 2013, 11:53
Exclamation How to study noise in CFX
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Mahmoud Gabr
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Dear all
Could you help my in how to study the noise generated in piping system containing orifice from induced vibration due to turbulence using CFX. I am working with SST model.

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M.Gabr
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Old   September 21, 2013, 06:21
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Glenn Horrocks
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What do you want to know about the noise? Are you looking for a full acoustics simulation (giving frequencies, acoustic dipoles and all that) or just a general idea if it is noisy or not?
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Old   September 26, 2013, 01:35
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Hi ghorrocks , thanks for your reply. I want to study the noise generated from turblance in order to optimize orifice design for low noise pressure reduction. this would require the frequencsies of waves generated due to pressure pulsation. But at first I want to know if this design is noisy or no. after that I may enter little bit deep study one of them.
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Old   September 26, 2013, 01:52
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Glenn Horrocks
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Getting the full acoustics spectrum from CFX is difficult - You are going to need to do LES to get that. You can get simple estimates from simple turbulence models and looking at the turbulent energy, but accurate data will require LES.
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Old   September 26, 2013, 02:51
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So ghorrocks , Which factors should I depend on in my preliminary study and comparing orifice designs using current turbulence model SST . and should I make it transient simulation or I can continue using steady state simulation
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Old   September 26, 2013, 06:23
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You could infer noise level from turbulence intensity on a steady state model. But be aware that this is a very crude guide only. The only way you are going to get accurate results from this is by a LES model, and that is quite an undertaking.
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Old   October 1, 2013, 14:53
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Dear ghorrocks.
I found That using LES model can't happen in steady state and require transient. Could you illustrate how to inspect the turbulence in steady state , I wouldn't go deeply in studding noise , only need indicator that this design would be better in generating noise due to turbulence.
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Old   October 1, 2013, 20:41
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Just a rough guess that turbulence intensity is linked to noise. So look at the turbulence intensity.

But you really should do some literature review on this to find the most appropriate way forwards.
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