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Nicolas April 3, 2007 04:51

AERODYNAMIC NOISE ANALYSIS
 
HI DOES ANY KNOW HOW TO PREDICT NOISE USING CFX. I READ THE AERODYNAMIC NOISE ANALYSIS PDF FILE IN THE MANUAL BUT I AM A BIT CONFUSED ON HOW TO USE CGNS FILES AND WHAT IS THE USEFULNESS OF DOING SO. IF ANY ONE KNOWS HOW TO DEAL WITH SUCH A PROBLEM OR HAS A TUTORIAL THAT SOMEONE CAN READ AND UNDERSTAND I WOULD APPRECIATE IT. THANK YOU NICK

Joe April 3, 2007 06:20

Re: AERODYNAMIC NOISE ANALYSIS
 
Must be noisy where you work.

Glenn Horrocks April 3, 2007 17:52

Re: AERODYNAMIC NOISE ANALYSIS
 
Nicolas,

CFX can predict the pressure waves which create noise and can therefore model noise generation. In practise, most people want the noise as some sort of sound pressure level at a significant distance away from the noise source, eg what dBA a few metres back from an engine in an infinite field. To model this you need a very fine mesh all the way to the measuring location and way past it so you don't get reflections. This is not practical in most cases.

I have heard that CFX can model the noise generation at the source and can be coupled to a package like SYSNOISE to calculate the distance and far-field effects.

Hope this helps.

Glenn

(Nice comment Joe!)

Nicolas April 4, 2007 01:32

Re: AERODYNAMIC NOISE ANALYSIS
 
Dear Glenn Thank you for your advice. I will have more detail look what SYSNOISE can do for my project.


Bak_Flow April 4, 2007 12:09

Re: AERODYNAMIC NOISE ANALYSIS
 
Nicolas and Glenn,

CFX does not have much for engineering noise predictions.

We can look at noise as consisting of 2 components:

1. broadband

2. tonal

Broadband is a result of pressure fluctuations in a turbulent flow ie jet noise, boundary layer noise, etc

Tonal is due to global unsteadyness in the flow due to blades passing, structures flapping, etc.

What Glenn is talking about is the near field pressure distribution from an UNSTEADY flow simulation. The issue then is how these near-field pressures relate to sound pressure levels at some distance as Glenn points out. The link between the 2 is what sysnoise could provide.

Fluent has some models as well so check that out if you get a chance.

Regards,

Bak_Flow


longbow April 4, 2007 12:41

Re: AERODYNAMIC NOISE ANALYSIS
 
CFX-Post 11 has a noise macro to calculate tonal noise generated by rotating blades based on Lowson equation.


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