FORCED OSCILLATIONS OF NONSPHERICAL BUBBLES

Abstract.- Various aspects of an oscillating bubble are presented. The general formulation and the linear spherical oscillation are discussed first followed by a corresponding variational treatment. Nonlinear subharmonic spherical oscillations and nonspherical oscillation are presented next. The study of nonspherical oscillation leads to a discussion on nonlinear Mathieu equation. Finally, the variational method is employed for the study of the coupling between subharmonic spherical oscilla-tion and nonspherical oscillation through nonlinear interaction. Experimental implication of the nonlinear coupling is briefly discussed. 1. INTRODUCTION.- A bubble in a liquid is a fasci-nating classical oscillator, all the more because it is an ordinary, visually observable physical object. It can execute simple harmonic, small am-plitude, spherical oscillations with well-define