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Old   April 21, 2008, 19:22
Default whistling through a pipe
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cfd-student
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Hi guys

I wanna whistle through a pipe and analyse the acoustical behaviour. What sort of boundary conditions i would need to do that. How much pressure do you recommend I should apply at the inlet (any value will do, its just an approximation).

Can you please direct me to any reading material on the subject. Thank you
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Old   April 21, 2008, 20:41
Default Re: whistling through a pipe
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Rogerio Fernandes Brito
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Does CFX make this kind of simulation? Why a whistle and not a shout?
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Old   April 22, 2008, 05:41
Default Re: whistling through a pipe
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cfd-student
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Ok lets simulate a shout. what will be my boundary condition and how much pressure should I apply at the inlet. CFX should be able to do such simulations because sound is nothing but pressure fluctuations within fluid.

cfd-student
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Old   April 22, 2008, 19:05
Default Re: whistling through a pipe
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Glenn Horrocks
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Hi,

Yes, CFX can do this type of simulation.

How are you going to excite the flow? Are you going to go the whole hog and model vortex shedding to generate the waves (like blowing across the top of a milk bottle or playing a recorder) or are you going to do the easy approach and just impose a varying pressure or velocity boundary? This will determine how complex the model must be.

The other end of the pipe is pretty easy. It is either closed or open and both are simple to model and mesh.

Glenn Horrocks
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Old   April 23, 2008, 05:51
Default Re: whistling through a pipe
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cfd-student
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Hi Glenn

I wanna impose time varying BC at the inlet and feed the points from a text file. How do I do that? Thanks
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Old   April 24, 2008, 01:01
Default Re: whistling through a pipe
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Glenn Horrocks
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Hi,

Set the inlet boundary as a pressure or velocity boundary where the condition is set by a CEL expression. Then setup a 1D interpolation function using the points from your test file.

Glenn Horrocks
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Old   April 24, 2008, 05:30
Default Re: whistling through a pipe
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cfd-student
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I do not have an expression however i have made up some numbers to use as a text file. I created a profile as was instructed in documentation (more and less) and then fed that into my inlet BC as "total pressure". It worked fine but it did not give me a standing wave I was expecting. Any ideas? Thank you
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