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

Reynolds · February 24, 2011, 05:37

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

Vinicius · February 25, 2011, 12:22

You must create those surfaces inside the model as internal interaces and use them as permeable surfaces in the FW-H model.

Reynolds · February 28, 2011, 15:27

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

Reynolds · February 28, 2011, 15:30

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

Vinicius · February 28, 2011, 15:40

That´s correct. Once you create the interface between the boundaries they don´t have anymore their properties, but the interface ones...

So, for your permeable surface, select the internal interface you´ve created.

kamal tewari · December 12, 2016, 08:53

Hi Reynolds

How were you able to calculate the overall sound pressure levels ? can you explain as I am modelling the jet noise and is facing similar problems.

fedora · December 13, 2019, 02:36

Can you please tell me where do you find the tutorial CCM+ on using the FW-H analogy for aeroacoustics? Thank you.

February 24, 2011, 05:37	Seeting up Permeable Surfaces for use with FW-H Acoustics in CCM+	#1
Reynolds New Member Matt Hollins Join Date: Nov 2010 Posts: 9 Rep Power: 15	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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February 25, 2011, 12:22		#2
Vinicius Member Vinicius Girardi Join Date: Mar 2009 Location: Sao Paulo, Brazil Posts: 80 Rep Power: 17	You must create those surfaces inside the model as internal interaces and use them as permeable surfaces in the FW-H model.

February 28, 2011, 15:27		#3
Reynolds New Member Matt Hollins Join Date: Nov 2010 Posts: 9 Rep Power: 15	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

February 28, 2011, 15:30		#4
Reynolds New Member Matt Hollins Join Date: Nov 2010 Posts: 9 Rep Power: 15	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

February 28, 2011, 15:40		#5
Vinicius Member Vinicius Girardi Join Date: Mar 2009 Location: Sao Paulo, Brazil Posts: 80 Rep Power: 17	That´s correct. Once you create the interface between the boundaries they don´t have anymore their properties, but the interface ones... So, for your permeable surface, select the internal interface you´ve created.

December 12, 2016, 08:53		#6
kamal tewari Member Polard Join Date: Oct 2015 Posts: 31 Rep Power: 10	Hi Reynolds How were you able to calculate the overall sound pressure levels ? can you explain as I am modelling the jet noise and is facing similar problems.

December 13, 2019, 02:36		#7
fedora New Member Federica Fregosi Join Date: Mar 2019 Posts: 3 Rep Power: 7	Can you please tell me where do you find the tutorial CCM+ on using the FW-H analogy for aeroacoustics? Thank you.