Time-domain simulation of acoustic scattering and internal propagation from multiple gas bubbles

Abstract

Acoustic scattering and resonance responses from multiple gas bubbles are computed using a time-domain simulation based on the numerical solutions of the conservation laws. The time histories of scattered pressure and velocity, both outside and inside the bubbles, are obtained simultaneously from an immersed-boundary method facilitating the investigation of both exterior and interior acoustic fields for non-spherical bubbles. Agreement is found with both analytical scattering solutions and those from empirical shape factors in limiting cases. In addition, the time-domain method allows for the study of the transient acoustic scattering from pulse forcing (Gaussian). In this case, the interior gas oscillates in an off-center, non-uniform manner compared to the steady state forcing cases. The time history and the interior gas behavior are presented in detail for combinations of two bubbles of different sizes and shapes (spherical, prolate, oblate). A comparison and analysis of this immersed-boundary method to the finite element method and boundary element methods is provided. Also, the increasingly important role of computational acoustics in the study scattering of multiple targets of diverse sizes and shapes is highlighted.