How to study noise in CFX

MGabr · September 20, 2013, 12:53

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.

best regards
M.Gabr

ghorrocks · September 21, 2013, 07:21

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?

MGabr · September 26, 2013, 02:35

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.

ghorrocks · September 26, 2013, 02:52

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.

MGabr · September 26, 2013, 03:51

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

ghorrocks · September 26, 2013, 07:23

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.

MGabr · October 1, 2013, 15:53

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.

ghorrocks · October 1, 2013, 21:41

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.

September 20, 2013, 12:53	How to study noise in CFX	#1
MGabr Member Mahmoud Gabr Join Date: Aug 2012 Location: Egypt Posts: 30 Rep Power: 14	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. best regards M.Gabr

September 26, 2013, 07:23		#6
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,852 Rep Power: 144	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. MGabr likes this.

October 1, 2013, 21:41		#8
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,852 Rep Power: 144	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. MGabr likes this.

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September 21, 2013, 07:21		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,852 Rep Power: 144	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?

September 26, 2013, 02:35		#3
MGabr Member Mahmoud Gabr Join Date: Aug 2012 Location: Egypt Posts: 30 Rep Power: 14	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.

September 26, 2013, 02:52		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,852 Rep Power: 144	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.

September 26, 2013, 03:51		#5
MGabr Member Mahmoud Gabr Join Date: Aug 2012 Location: Egypt Posts: 30 Rep Power: 14	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

October 1, 2013, 15:53		#7
MGabr Member Mahmoud Gabr Join Date: Aug 2012 Location: Egypt Posts: 30 Rep Power: 14	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.