Acoustic cavitation, description

Instead, sonochemistry and sonoluminescence derive principally from acoustic cavitation, which serves as an effective means of concentrating the diffuse energy of sound. Compression of a gas generates heat. When the compression of bubbles occurs during cavitation, it is more rapid than thermal transport, which generates a short-lived, localized hot-spot. Rayleigh s early descriptions of a mathematical model for the collapse of cavities in incompressible liquids predicted enormous local temperatures and pressures.13 Ten years later, Richards and Loomis reported the first chemical and biological effects of ultrasound.14... 

It should be noted that acoustic irradiation is a mechanical energy (no quantum), which is transformed to thermal energy. Contrary to photochemical processes, this energy is not absorbed by molecules. Due to the extensive range of cavitation frequencies, many reactions are not well reproducible. Therefore, each publication related to the use of US generally contains a detailed description of equipment (dimensions, frequency used, intensity of US, etc.) [709]. Sonochemical reactions are usually marked )))), in accordance with internationally accepted usage [708], For successful application of US, the influence of various factors can be summarized as follows [710] ... 

A more illustrative description of the bubble motion in an acoustic field can be introduced by the concept of cavitation thresholds for different types of bubble behavior. Depending on the nature of the motion four basic types of cavitating voids are distinguished stable cavitation, rectified diffusion, dissolving bubbles, and transient cavitation. 

As we will see later, the Rayleigh-Plesset description closely matches the actual radial behavior of a bubble as long as the non-radial deformations are small (or of short duration). Since the behavior of a bubble depends on the applied acoustic pressure, Apfel estimated the threshold associated to transient cavitation. A part of this threshold is, of course, common to the Blake threshold (explosive growth of a cavitation nucleus. Fig. 14). 

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