Study On Nonlinear Sound Propagation Characteristics In Bubbly Liquids Based On Effective Medium Method

Bubbly liquids are widely found in nature.Due to the large difference in the density,acoustic impedance and compression ratio of air and water,the acoustic properties of the mixed medium are significantly changed,which has a great influence on the propagation of sound waves.With the wider application of underwater high-power and high-intensity acoustic source equipment,forcing the study of nonlinear acoustic theory to be more in-depth.In this paper,the equivalent medium model of bubbly liquids is established by using the equivalent medium method.Based on the dynamic equation of bubbles,the dynamic characteristics of bubbles are studied,and the vibration equations of the volume form of bubbles under the second and third order approximations are derived.The acoustic characteristics of bubbly liquids are studied from the scattering and absorption cross sections of bubbles,the dispersion characteristics of sound velocity and attenuation,and the equivalent non-linear parameters of bubbly liquids.The non-linear wave equation of the bubbly liquids is deduced by using the equivalent parameter of equivalent density.In order to study the interaction between the non-linear sound field and the non-linear vibration of bubbles in the propagation of sound waves in bubbly liquids,a finite difference numerical method is proposed to comprehensively study bubble vibration equation and nonlinear wave equation.The correctness of the numerical algorithm is proved by comparing the numerical method with the Bessel-Fulbini solution,the westervelt equation and the analytical solution.The finite difference numerical algorithm is used to study the non-linear propagation law of single-frequency acoustic wave,double-wave interaction,pulse interaction,chirp interaction and single-frequency and broadband interaction in bubbly liquids.Finally,in order to further verify the correctness of the numerical algorithm,the acoustic propagation experiments in bubbly liquids are carried out.The correctness of the numerical algorithm is proved by comparing the sum and difference frequencies of the measured two-wave excitation with the simulation results.