Nonlinear Acoustic Waves in Liquids with Gas Bubbles: A Review

This brief abstract historical review consists of two parts. Linear and weakly nonlinear oscillations of bubbles in acoustic field are considered in the first part. Basic data are presented on the following unusual properties of gas–liquid medium: very low speed of sound; high scattering cross section and large wavelength at the resonant frequency in comparison with the bubble radius; and high Q factor, which is determined by the loss on sound emission. The equation for small induced oscillations in acoustic field and the dispersion equation for the compressibility of the medium are presented. It is indicated that the effective nonlinearity of the medium may exceed by three orders of magnitude the nonlinearities of both liquid and gas taken separately. Some applications of small oscillations of bubbles in hydroacoustics, medicine, and linear and nonlinear diagnostics are described. The phenomena of significant changes in the sizes of bubbles, including their creation and collapse, are discussed in the second part. The sonoluminescence of a group of bubbles and a single bubble is described. Some facts related to the unbounded cumulation and its limiting factors are indicated. The history of attempts to implement “sonofusion” (thermonuclear reaction under collapse of cavitation bubbles) is outlined.