Linear Acoustic Properties of Bubbly Liquids Near the Natural Frequency of the Bubbles Using Numerical Simulations

We consider the problem of determining linear acoustic properties of bubbly liquids near the natural frequency of the bubbles. Since the effective wavelength and attenuation length are of the same order of magnitude as the size of the bubbles, we devise a numerical scheme to determine these quantities by solving exactly the multiple scattering problem among many interacting bubbles. It is shown that the phase speed and attenuation are finite at natural frequency even in the absence of damping due to viscous, thermal, nonlinear, and liquid compressibility effects, thus validating a recent theory (Sangani 1991). The results from the numerical scheme are in good agreement with the theory but considerably higher than the experimental values for frequencies greater than the natural frequency. The discrepancy with experiments remains even after accounting for the effect of polydispersity, finite liquid compressibility, and non-adiabatic thermal changes.