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Cavitation
Name: David S.
Status: Student
Age: 18
Location: N/A
Country: N/A
Date: N/A
Question:
Can cavitation or a similar effect be created in a
substance (water)with the use of sound waves that come from a source
other than the mechanical disturbance from surfaces such as the prop or
other parts that are highly frictional? (in other words can sound waves
transmitted through a surface ((of a submarine for instance)) with little
friction produce cavitation?)
Replies:
Yes, an object vibrating with enough amplitude at the correct (typically
ultrasonic) frequency will also cause cavitation in a liquid. The amplitude
of vibration does not have to be very large - less than an millimeter will
do.
Richard E. Barrans Jr., Ph.D.
Assistant Director
PG Research Foundation, Darien, Illinois
Yes. Anything that can make a big enough local reduction in pressure can
cause cavitation.
Tim Mooney
Ultrasonic transducers are commonly used in laboratories to produce
cavitations for many applications, especially for making dispersions and for
breaking open cells of various types.
The U.S. Navy is conducting research for using cavitations to "encapsulate"
entire submarines in a cavitations bubble that would allow much faster
speeds than presently available, maybe 100 mph. See:
http://www50.dt.navy.mil/facilities/LCC.html
In the last year, maybe two, Scientific American described the use of
ultrasonic reverse echo technology to produce highly amplified and
concentrated beams of acoustic energy for precision non-invasive surgery.
Roughly the principle is: from a focus point generate a weak signal of
acoustic energy. This is picked up by an array of transducers surrounding
the patient. Store the signals digitally, amplify them, then send them back
to the focus reversed "first-in-last-out" fashion, rather than the
"first-in-first-out" way conventional echoes occur. This refocuses the
acoustic energy precisely at its original source, but with much higher
amplitude that kills the cells at the source, but not in nearby tissue
because the convergence in not sufficient to cause cell damage except at the
precise point where the acoustic wave originated.
Vince Calder
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Update: June 2012
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