Aeroacoustics Scaling laws

AS_Aero · February 19, 2019, 10:21

Hi
Is there anybody having experience in scaling laws for Aeroacoustics ?

I have to do some aeroacoustics simulation for huge piping system of 2.5m diameter and different bends and pipe lenghts of 100m. (its like a huge industrial hvac system ) and now I want to measure the noise generated from it and noise sources etc. But firstly I want to know if I can scale down the entire system from meters to centimeter so that I can do the simulation with reduced computational power. And then in the case of Acoustics I will need some scaling law as well. So I am not sure if there is any possibility for that as well.
Kindly let me know if anyone has experience in that.

LuckyTran · February 19, 2019, 13:53

Geometry scaling will not save you any computational cost. To save computational cost, you have to reduce the actual size of the problem and/or reduce complexity (less equations, etc).

The flow stuff scales like Reynolds number and mach number. The acoustics stuff scales like Helmholtz number. For these difficulties, industry people say acoustics is unscalable.

AS_Aero · February 20, 2019, 08:07

Dear Lucky Tran

Thanks a lot for your reply.

LuckyTran · February 20, 2019, 14:42

And in case it was not obvious, you can also just use a coarser mesh with fewer cells. The number of cells and number of equations is what determines computational cost. It doesn't matter whether these cells are 1 pm, 1nm, 1mm, 1m, 1km, or 1AU in size.

February 19, 2019, 10:21	Aeroacoustics Scaling laws	#1
AS_Aero Senior Member Join Date: Mar 2013 Location: Germany Posts: 357 Rep Power: 14	Hi Is there anybody having experience in scaling laws for Aeroacoustics ? I have to do some aeroacoustics simulation for huge piping system of 2.5m diameter and different bends and pipe lenghts of 100m. (its like a huge industrial hvac system ) and now I want to measure the noise generated from it and noise sources etc. But firstly I want to know if I can scale down the entire system from meters to centimeter so that I can do the simulation with reduced computational power. And then in the case of Acoustics I will need some scaling law as well. So I am not sure if there is any possibility for that as well. Kindly let me know if anyone has experience in that.

February 19, 2019, 13:53		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,747 Rep Power: 66	Geometry scaling will not save you any computational cost. To save computational cost, you have to reduce the actual size of the problem and/or reduce complexity (less equations, etc). The flow stuff scales like Reynolds number and mach number. The acoustics stuff scales like Helmholtz number. For these difficulties, industry people say acoustics is unscalable. Last edited by LuckyTran; February 20, 2019 at 10:16.

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February 20, 2019, 08:07		#3
AS_Aero Senior Member Join Date: Mar 2013 Location: Germany Posts: 357 Rep Power: 14	Dear Lucky Tran Thanks a lot for your reply.

February 20, 2019, 14:42		#4
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,747 Rep Power: 66	And in case it was not obvious, you can also just use a coarser mesh with fewer cells. The number of cells and number of equations is what determines computational cost. It doesn't matter whether these cells are 1 pm, 1nm, 1mm, 1m, 1km, or 1AU in size.