Bubble oscillations driven by aspherical ultrasound in liquid

In this paper we study the bubble dynamics driven by an aspherical acoustic field, based on the theory of hydrodynamics. Evolution equations for an aspherical bubble are derived under the aspherical acoustic driving. The numerical calculations show that the aspherical bubble can oscillate stably and periodically under suitable conditions, which is out of the explanation of spherical perturbation theory. Furthermore, under some controlling parameters, the aspherical distortion can either grow rapidly, leading to the bubble's breakdown, or decay gradually making the bubble spherical, which is similar to the result of the perturbation theory driven by a spherical ultrasound. (C) 2003 Acoustical Society of America.