Sonar experts: How much sound crosses a layer?

[drEaPer]

Originally Posted by Wim Libaers

No, the reason for cavitation is not a chemical reaction where water decomposes (but chemical reactions might happen as a consequence of the high temperature reached when bubbles collapse during cavitation). It simply is that, at high flow speeds, pressure is reduced, so dissolved air will easily go out of solution, and water will boil at lower than normal temperatures. This is also why cavitation is less likely to happen when deep: the pressure is much higher, so (at the same temperature) you need a much faster flow to lower te pressure enough to start the boiling. It obviously also becomes easier with increasing temperature.

Of course, as soon as the bubbles come into a region of slower flow, they are not stable and will collapse. This is noisy and may damage the screw.

Thats what I said. Dunno how that chemical stuff comes up, I didnt say anyhting about that. I said mechanical (A spinning prop being the mechanical force creating a vacuum because the flow cannot keep up with the pace, therefore reducing the pressure which produces bubbles). My point was, that there is, and always will be air in h2O! Anyhow, thx for more input