D4RR3N
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Water resonating in cylinder
This in more a physics question rather then a chemistry question.
I want to calculate the resonant frequency of a closed ended cylinder. I found this online calculate below which will do this for air but I want to
use water not air ie a jet of water passing over the top of the cylinder whilst submerged. Can I use the same calculator by altering the speed of
sound value?
http://hyperphysics.phy-astr.gsu.edu/hbase/waves/clocol.html
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watson.fawkes
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Quote: Originally posted by D4RR3N  | | I want to calculate the resonant frequency of a closed ended cylinder. I found this online calculate below which will do this for air but I want to
use water not air ie a jet of water passing over the top of the cylinder whilst submerged. Can I use the same calculator by altering the speed of
sound value? |
Maybe. The math is the same insofar as the math goes, but that may not be all that's going on.
Whether the math applies correctly to the physical setup you have is a different question.
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D4RR3N
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| Quote: Originally posted by watson.fawkes | | Maybe. The math is the same insofar as the math goes, but that may not be all that's going on. Whether the math applies correctly to the physical
setup you have is a different question. |
The problem is I cant find any info on this in regards to an equation for a water filled cylinder. I feel that a water filled cylinder will resonate
at a lower frequency to the same cylinder filled with air.
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phlogiston
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The resonant frequency of the tube will be higher, not lower. The frequency is proportional to the speed of sound in the medium, in this case water.
For a tube closed at one end:
f= n*v / (2*L)
where n = the resonance node (1,2,3,etc.)
L=length of tube
v= speed of sound
However, I have no idea if the principle of generating an oscillation by blowing a jet of water across the open end will work. In air, this works but
why is a mystery to me. Possibly, it may involve certain aspects of turbulent flow, viscosity, ? that work differently in water.
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Twospoons
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It may not work at all due to water being essentially incompressible.
Helicopter: "helico" -> spiral, "pter" -> with wings
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watson.fawkes
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| Quote: Originally posted by D4RR3N | | I feel that a water filled cylinder will resonate at a lower frequency to the same cylinder filled with air. |
Good thing there's math then. See phlogiston's answer. | Quote: Originally posted by phlogiston | | However, I have no idea if the principle of generating an oscillation by blowing a jet of water across the open end will work. In air, this works but
why is a mystery to me. Possibly, it may involve certain aspects of turbulent flow |
It's a combination of
turbulent flow, which has a wide range of frequency components, and the tube acting as a resonant filter, which preferentially oscillates at certain
frequencies. The "Q" of the tube as an oscillatory cavity is frequency dependent and determines the timbre of the sound in the tube. It's not the case
that the only motions in a driven oscillator system are at the resonant frequencies, but these frequencies do have the highest amplitudes. There will still be a resonant
frequency for the combination of the cavity and the medium. I agree with your implicit point that this may not be relevant at all.
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