CAVITATION, is a violent agitation of a liquid caused by the rapid formation and collapse of vapor bubbles. It occurs when the liquid’s pressure fluctuates slightly above and below its vapor pressure, as may happen in the vicinity of a ship’s propeller or in the working fluid of hydraulic machinery. Cavitation results when a liquid moves rapidly from a region of lower fluid pressure, where it vaporizes and forms vapor bubbles (cavities), to a region of higher pressure, where the bubbles collapse forcefully.
Cavitation can pit metal parts and danger-ously weaken them, and it also can reduce the efficiency of pumps, turbines, ship propellers, and other hydraulic machinery. It is sometimes accompanied by a noticeable noise arising from the formation and collapse of the bubbles. Cavitation noise is a handicap in naval actions because it facilitates the detection of a ship or submarine by the enemy’s sonar.