Cavitation bubbles – the good, the bad and the beautiful

A sudden decrease in pressure triggers the formation of vapor and gas bubbles inside a liquid medium (also called cavitation). This leads to many (key) engineering problems: damage of the nearby surfaces, noise and vibration of hydraulic machinery. Even the propulsion of space launchers is limited by the conditions that trigger cavitation in fuel turbopumps. On the other hand, cavitation is a potentially a useful phenomenon: the extreme conditions are increasingly used for a wide variety of applications such as surface cleaning, enhanced chemistry, and waste water treatment (bacteria eradication and virus inactivation). Despite cavitation is intensively studied since the time of Newton, a large gap persists between the understanding of the mechanisms that contribute to the effects of cavitation and its application – in the last years advanced experimental and numerical techniques enable more and more detailed insights into the phenomenon, but we are still not able to answer the fundamental question: What precisely are the mechanisms how bubbles can damage materials, clean, disinfect, kill bacteria and enhance chemical activity?