Modal impedances for two spheres in a thermoviscous fluid

Abstract

A modal impedance matrix is formulated for two spheres undergoing axisymmetric oscillations in a thermoviscous acoustic medium. The formulation utilizes the governing equations of Epstein and Carhart [J. Acoust. Soc. Am. 25, 553–565 (1953)] and the analysis method of Guz and Golovchan [Diffraction of Elastic Waves in Multiply Connected Bodies (U.S. Department of Commerce, Washington, DC, 1973)]. The impedance matrix is used to generate dilatational and translational surface-force curves for dilatational and translational surface motion. Three models of the acoustic medium are examined: full thermoviscous, thin boundary layer, and ideal acoustic. Numerical results for water and air display the limitations of the last two models.