Volume 107, Issue 1, January 2000
Index of content:
- NONLINEAR ACOUSTICS 
107(2000); http://dx.doi.org/10.1121/1.428296View Description Hide Description
Key to the dynamics of the type of bubble collapse which is associated with such phenomena as sonoluminescence and the emission of strong rebound pressures into the liquid is the role of the liquid inertia. Following the initial formulation of the collapse of an empty spherical cavity, such collapses have been termed “Rayleigh-like.” Today this type of cavitation is termed “inertial,” reflecting the dominant role of the liquid inertia in the early stages of the collapse. While the inertia in models of spherical bubble collapses depends primarily on the liquid, experimental control of the liquid inertia has not readily been achievable without changing the liquid density and, consequently, changing other liquid properties. In this paper, novel experimental apparatus is described whereby the inertia at the early stages of the collapse of a conical bubble can easily be controlled. The collapse is capable of producing luminescence. The similarity between the collapses of spherical and conical bubbles is investigated analytically, and compared with experimental measurements of the gas pressures generated by the collapse, the bubble wall speeds, and the collapse times.
107(2000); http://dx.doi.org/10.1121/1.428346View Description Hide Description
A mean force exerted on a small rigid sphere by a sound wave in a viscous fluid is calculated. The force is expressed as a sum of drag force coming from the external steady flow existing in the absence of the sphere and contributions that are cross products of velocity and velocity derivatives of the incident field. Because of the drag force and an acoustic streaming generated near the sphere, the mean force does not coincide with the acoustic radiation pressure, i.e., the mean momentum flux carried by the sound field through any surface enclosing the sphere. If the sphere radius R is considerably smaller than the viscouswave penetration depth δ, the drag force can give the leading-order contribution (in powers of to the mean force and the latter can then be directed against the radiation pressure. In another limit, the drag force and acoustic streaming play a minor role, and the mean force reduces to the radiation pressure, which can be expressed through source strengths of the scatteredsound field. The effect of viscosity can then be significant only if the incident wave is locally plane traveling.