cavitointi

Cavitointi, commonly translated as cavitation, is the formation, growth and collapse of vapor-filled cavities in a liquid that arise when local pressure falls below the liquid’s vapor pressure. This phenomenon occurs in flowing systems where rapid acceleration or turbulence creates regions of very low static pressure, allowing tiny vapor bubbles to nucleate. The bubbles can persist and oscillate (stable cavitation) or undergo rapid inertial growth and violent collapse (inertial or transient cavitation) when they enter higher-pressure zones. The collapse generates high local temperatures and pressures, along with microjets and shock waves, which can erode solid surfaces and produce noise and vibration.

Cavitation is a concern in hydraulic machinery such as pumps, propellers, turbines and piping, where it reduces efficiency and can cause pitting, material damage and premature wear. It can also be produced deliberately in processes such as ultrasonic cleaning, sonochemistry, emulsification and medical therapies using focused ultrasound, where cavitation enhances chemical effects or tissue disruption.

Detection and monitoring rely on acoustic emissions, vibration analysis and high-speed imaging to identify incipient cavitation and its severity. Mitigation strategies include increasing the local pressure or reducing the low-pressure region by raising net positive suction head (NPSH), slowing flow, altering geometry, smoothing surfaces, applying erosion-resistant materials or coatings, and selecting operating conditions that stay above the cavitation inception threshold. In some applications, controlled cavitation is used to promote chemical reactions or therapeutic effects.

Historically, cavitation has been studied since the 19th century and is explained by bubble dynamics described in early fluid mechanics. It remains a central consideration in fluid machinery design and in emerging ultrasonic and biomedical applications.