A question on boundary condition

[wuchaoqun]

I am analyzing the ultrasonic sound pressure in a pipe. As mentioned in many references, when the metal pipe has a enough thick wall, it can be looked as a rigid boundary! Any boby can tell me how thick is thick enough!?

 

[krishi1978]

hi,
as far as i know, if u r considering the pipe wall as a rigid body, what ever the thickness value u will give does not matter. But how ever, depending on the diameter of the pipe u can find the DIN standard thickness for the pipe..and depend on the value u can assign the thickness..

regards,
Krishi

 

[EricZhao]

It would depend on the pipe's configuration (Length, diameter, end condition). I would say as long as the pipe's natural frequency does not fall in the working ultrasound frequency, and the pipe is reasonably solid. It should be able to be considered as rigid boundary.

 

[wuchaoqun]

thanks for your post ,firstly. But i donot agree with you.
i have carried out a experiment. A acrylic pipe, is not a resonance dimension . and i think it is reasonably solid . but the distribution of sound pressure in the pipe is in agreement with the theoretical value of soft boundary!

 

[GregLocock]

Well, then, you seem to know the answer.

Cheers

Greg Locock

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

 

[wuchaoqun]

but i do not know how to set up a rigid boundary condition? would you pls give me some hints?