| Topic: |
Science > Physics |
| User: |
"heiko ackermann" |
| Date: |
23 Mar 2005 03:03:06 PM |
| Object: |
cavitation threshold |
hey,
if create acoustical cavitation in a liquid i must use ultrasound iwth an
amplitude higher than the spcific cavitation threshold.
Is it now possible after the succesfully creating of the cavitation, to
reduce the sound wave pressure under this specific cavitation threshold
without stopping the cavitation process.
In think yes, because the created cavitation bubbles will reduce the
cavitation threshold extremly.
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| User: "tj Frazir" |
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| Title: Re: cavitation threshold |
23 Mar 2005 05:29:51 PM |
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Cavitation is not a acustic afect.
Thats the prop vacume sucking air from the furface instead of getting
water wile the engine reves up to the Gov.
Your transducer should tilt forward a bit so cavitation gap dont form
over the transducer face.
the cavitation threshold is how fast you can go and still look behind
you without cavitation vacume forming on the transducer.
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| User: "bz" |
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| Title: Re: cavitation threshold |
23 Mar 2005 07:02:57 PM |
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(tj Frazir) wrote in news:12699-4241FBEF-161
@storefull-3217.bay.webtv.net:
Cavitation is not a acustic afect.
Thats the prop vacume sucking air from the furface instead of getting
water wile the engine reves up to the Gov.
Your transducer should tilt forward a bit so cavitation gap dont form
over the transducer face.
the cavitation threshold is how fast you can go and still look behind
you without cavitation vacume forming on the transducer.
He was talking about cavitation as in ultrasonic sound induced cavitation.
You are talking about a different [though distantly related] phenomina.
Your form of cavitation persists as long as the prop is in motion at that
speed.
His form of cavitation is short term. The cavities form and collapse twice
in every Hz. There are indications that very high temperatures may exist
for very short times within those cavities.
--
bz
please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.
bz+sp@ch100-5.chem.lsu.edu remove ch100-5 to avoid spam trap
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| User: "tj Frazir" |
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| Title: Re: cavitation threshold |
25 Mar 2005 10:37:16 AM |
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Ultasound is a surface bump agaist the water and when it reqcoils there
is a gap between the surface and the water and that gap must close befor
you can hit the water again.
its still cavitation.
a vaccume created in water is cavitation.
what else would cavitation aply to ?
a boat going forward planes.
A falling rock has a vacume streak behind it.
A bullet blows a hole in the water.
It cavitates till it slows down.
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| User: "tadchem" |
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| Title: Re: cavitation threshold |
25 Mar 2005 01:33:25 PM |
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heiko ackermann wrote:
hey,
if create acoustical cavitation in a liquid i must use ultrasound
iwth an
amplitude higher than the spcific cavitation threshold.
Is it now possible after the succesfully creating of the cavitation,
to
reduce the sound wave pressure under this specific cavitation
threshold
without stopping the cavitation process.
In think yes, because the created cavitation bubbles will reduce the
cavitation threshold extremly.
Cavitation occurs when the local pressure (hydrostatic + hydrodynamic +
acoustic) drops below the equilibrium vapor pressure of the liquid at
the locar temperature: the liquid literally boils.
One can suppress cavitation by applying an external pressure (i.e. gas
pressure in a sealed container, or hydrostatic pressure by increasing
the depth of the fluid) or by reducing the acoustic amplitude so that
the negative acoustic pressure (pressure during the rarefaction portion
of the acoustic wave cycle) is insufficient to reduce total pressure
below the equilibrium vapor pressure.
HTH
Tom Davidson
Richmond, VA
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| User: "tj Frazir" |
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| Title: Re: cavitation threshold |
25 Mar 2005 04:11:06 PM |
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broach ...
102022.jpg
Address:http://www.strangedangers.com/images/content/102022.jpg
Changed:3:39 PM on Monday, August 23, 2004
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