Acoustic radiation force on a spherical particle in a viscous heat-conducting fluid .2. Force on a rigid sphere

The general expression derived in Part I of this study [J. Acoust. Soc. Am. 101, 713-721 (1997)] for the acoustic radiation force on a spherical particle immersed in a viscous heat-conducting fluid is applied here to the case of a rigid sphere. Three types of incident sound field are considered: a plane traveling wave, a plane standing wave, and a diverging spherical wave. To demonstrate dissipative effects on the force clearly, for each of these fields two limiting cases of interest are investigated. In the first of these, the sphere radius is assumed to be large compared with the viscous and thermal wavelengths in the surrounding fluid and the thermal wavelength inside the sphere. In the second case, the sphere radius is assumed to be small compared with the above wavelengths. In addition, in both cases, it is assumed that the sound wavelength is much larger than the above parameters. Since viscous effects have been examined in earlier papers by the present author, in this paper, the main attention is given to thermal effects. It is shown that these can drastically change the radiation force, resulting in, for example, the movement of light spheres both from the sound source and to it in a plane traveling wave and levitation in a diverging spherical wave. (C) 1997 Acoustical Society of America.