Definition of Cavitation
Cavitation is the rapid formation and subsequent collapse of vapor-filled bubbles or cavities within a liquid. This occurs when the local pressure of the liquid drops below its vapor pressure, causing the liquid to turn into vapor even at ambient temperatures.
The Process: Formation and Collapse
The process involves two main stages: First, vapor bubbles form in low-pressure zones, typically near rapidly moving surfaces like a boat propeller or pump impeller. Second, these bubbles quickly move into regions of higher pressure and violently collapse (implode), creating powerful shockwaves and microjets.
Practical Examples and Effects
A common example of cavitation is the pitting and erosion seen on marine propellers, pump impellers, and hydroelectric turbine blades. The implosion of the bubbles generates intense localized pressure waves that can cause significant material damage over time, along with characteristic noise and vibrations.
Importance and Prevention
Understanding cavitation is crucial for designing and operating fluid machinery efficiently and safely. Engineers work to prevent it by optimizing component shapes, using cavitation-resistant materials, and ensuring operating conditions (like flow velocity and pressure) avoid the critical cavitation threshold.