Response to Acoustic Excitation

[jas12345]

hi
what is the best way to model a cylindrical structure that will undergo SPL of 150db for 15 minutes?
i have a Ansys FEM modal analysis of the structure to 3000Hz.
i was thinking of working out the pressure from the 150db SPL and applying this to the external
surfaces of the structure and performing a response spectrum analysis to determine peak stresses.
for example, 150db, Pref=2e-5, so 150=20log(Prms/2e-5)
-> Prms = 632Pa
-> P=632 x sqrt(2) = 893Pa, is the pressure i would use.

does this seem sensible?
is there another better way of doing this?
also without doing a time domain transient type analysis what is the best way of
accounting for the 15 minutes duration?

the other option i was thinking was a fluid-structure analysis, with the fluid elements surrounding the structure and applying the 150db to the fluid & seeing what the response of the structure was.
but again i'm not sure how to 'apply the 150db load' to the fluid?

anyway might be an interesting discussion!
thanks!
jas

 

[GregLocock]

1) yes, but are you sure it is just the external surfaces?

2) don't think so

3) by looking at the s/n curve of your material

4) sounds unnecessarily complicated to me

Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[spongebob007]

Stupid question:

Do you have ANSYS Multiphysics? If the answer is yes, then you have acoustic fludi elements that have coupled pressure/displacement degrees of freedom. I have done acoustic FSI analysis in ANSYS before. It's been probably four years since I touched it so I can't give you much help in that regard but there is info in the ANSYS documentation that will point you in the right direction.