Modern Approaches to the Description of the Dynamics of Cavitation Bubbles and Cavitation Clouds

The article deals with the modeling of high-energy cavitation processes, such as shock waves, cavitation erosion, bubble glow (sonoluminescence), etc., in a high-intensity acoustic field. It is shown that the well-known model based on the Keller–Miksis and Bjerknes equations does not correspond to a number of experimental data obtained in the study of a “single” cavitation bubble pulsating motionlessly in the antinode of a standing wave and an “ordinary” bubble moving in a cavitation cloud. To eliminate these inconsistencies, a new system of equations is proposed, which additionally takes into account the nonequilibrium processes of vapor evaporation and condensation and the imperfection of the vapor–gas mixture in the bubble, as well as the translational motion of the bubble. It is shown that with rapid compression of the bubble, the vapor inside it does not have time to condense and strongly damps this compression. The resulting equation explains the strong dependence of the intensity of “single” bubble glow on the temperature of the liquid. Contradictions in the description of the translational motion of bubbles associated with the application of the Bjerknes equation are eliminated. It is shown that a translationally moving bubble is compressed much weaker than a stationary one, since in the compression phase the energy of the radial motion of the bubble flows into the energy of translational motion. This allows us to explain the reason for the difference in the mechanisms of light emission from bubbles of different types. A “single” bubble emits light at maximal compression due to heating of the vapor–gas mixture up to 5000–10 000 K. Bubbles in a cavitation cloud move progressively, and their glow, in the absence of strong compression, is caused by micro-discharges in the vapor–gas phase during deformation of the bubble surfaces.