ABSTRACT
Cavitation, the rupture of liquids and its associated effects, is a much more general phenomenon than that caused by the propagation of an intense ultrasonic wave in a liquid. It can be engendered hydrodynamically (ship’s propellers, turbines, etc.), by absorption of a laser beam, or by the passage of elementary particles in a liquid, among other possibilities. Indeed, the subject became of interest to the British Royal Navy in the late 19th century due to rapid propeller erosion of its warships. The importance of the damage ultimately led to the general study of the implosion of a liquid in an empty spherical cavity carried out by Lord Rayleigh in 1917. However, we are particularly interested in acoustic cavitation here not only because of its intrinsic interest as an acoustic phenomenon in its own right but also because of its present and potential applications. These are due, in part and principle, to the controlled erosion of nearby surfaces caused by collapsing bubbles, leading to ultrasonic cleaning, machining, etc. Other applications are in the medical area (hypothermia, lithotripsy, and the associated dosimetry concerns), sonochemistry, emulsification, etc. The actual mechanism is still incompletely understood, and in different cases almost certainly involves shock waves, imploding liquid jets, and the high temperatures and pressures associated with bubble collapse. The effect is demonstrably efficient; in some cases, one single bubble collapse is sufficient to create a deep cavitation pit.
