>>Harmonic multiplication of such forces is a well-understood phenomenon, and, as you've pointed out, can result in >spectacular failures.
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>You are right that the consequences of the phenomenon are well understood, but I have yet to see a mathematical model that comes up with more than half of the energy required to give the resultant failure, there has been a lot of research on this subject, and a lot of head scratching but no definitive answer.

Force(s) cause the failure, not energy - they are two different things.

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>>My understanding is that propellor cavitation damage is caused by sonoluminescence, the effects of which have been >understood for some time now: http://en.wikipedia.org/wiki/Sonoluminescence . Fundamentally, this is another >example of harmonics/resonance.
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>With prop cavitation it is caused not by standing wave stimulation but by incorrect fairing of the blade, it can be removed by reshaping/fairing.
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>Just a couple of things I would like to point out:
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>1. It has been proven that the period of between 35 and a few hundred picoseconds life cycle of the bubble rules out any nuclear type process as the period is to short for such processes to occur.
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>2. In the instance of the prop cavitation, which is a bubble of super heated steam, where does the energy come from to heat the gas to above 20,000K+, remember to get water from room temperature to 20,000K+ involves GJoules of energy per KG, once again the numbers don't add up, and I ask where does all this energy come from.

The heated mass is tiny - according to the article the bubbles are ~1 micron in diameter - and the time duration at high temperature is extremely short. I don't know how you came up with the mass of a bubble in your calculations but it doesn't seem unreasonable to me that the total energy required is not that large. The article has a picture of sonoluminesence created by an ultrasonic horn; it would be interesting to know its power input but I don't imagine it's in the MW or GW range.

The key to sonoluminesence seems not to be the total amount of energy involved, but rather its intensity. That's what makes it of interest to researchers seeking nuclear fusion.