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The Rise of Life on Earth: Cavitation in Nature
okozyuk.com
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Abstract
The phenomenon of cavitation has been known in science and technology for more than a hundred years. It was first recognized as an important hydrodynamic phenomenon in connection with high speed marine propulsion, including early observations associated with British destroyers in the late nineteenth century. Osborne Reynolds and later researchers helped establish cavitation as a serious problem in ship propellers, pumps, and turbines [1,2].
Cavitation and Ordinary Boiling
Cavitation is different from ordinary boiling. In ordinary boiling, a liquid changes into vapor because its temperature rises to the boiling point. In cavitation, the liquid may remain at nearly the same temperature, but the local pressure drops sharply. When the pressure becomes low enough, the liquid vaporizes and microscopic vapor bubbles appear [1,2].
This can happen when a liquid flows rapidly around an object, through a narrow passage, across a propeller blade, over rocks in a stream, or through sudden changes in elevation. The relative velocity of the flow causes local pressure to drop. If that pressure approaches the saturated vapor pressure of the liquid, vapor cavities form.
These cavitation bubbles are usually short lived. When they move into a region of higher pressure, they collapse violently. During collapse, the vapor inside the bubble condenses, and the surrounding liquid rushes inward. This collapse can generate shock waves, high speed liquid microjets, intense local heating, and strong chemical effects [4–6].