What problem occurs on propeller blades when water pressure drops too low, causing vapor bubbles to form and collapse?

The problem that occurs on propeller blades when water pressure drops too low, causing vapor bubbles to form and collapse, is called cavitation. Cavitation is the phenomenon where rapid changes in pressure within a liquid lead to the formation of small vapor-filled bubbles, or cavities, which then violently collapse. On a propeller blade, as it rotates through the water, its hydrodynamic shape causes the water to accelerate over certain surfaces, particularly the suction side. According to Bernoulli's principle, this increase in water speed results in a significant drop in localized pressure. When this localized pressure drops below the water's vapor pressure—the specific pressure at which water changes into vapor at a given temperature—tiny vapor bubbles instantly form in the water. As these bubbles are carried by the water flow into areas of higher pressure, they become unstable and rapidly implode, or collapse. This violent implosion generates extremely localized and intense shockwaves and high-speed micro-jets of water. Repeated impacts from these collapsing bubbles cause severe physical damage to the propeller blade material over time, a process known as cavitation erosion. This erosion manifests as pitting, material removal, and eventual fatigue, which reduces the propeller's efficiency, thrust, and lifespan, while also increasing noise and vibration.