Acoustic radiation pressure produced by a beam of sound

Abstract

The second-order force produced by a sound beam directed normally at a plane target is calculated. Previous theories on acoustic radiation pressures associated with plane acoustic waves are examined critically and erroneous results, where they exist, are noted and rectified. A number of general relations are established using a new approach which avoids the necessity of dealing with detailed solutions of the governing nonlinear equations. Some of the concepts inferred from known solutions obtained by previous authors require drastic revision in the light of the present study. Specifically, the notion that Rayleigh radiation pressure depends on the nonlinearity of the medium (while Langevin radiation pressure does not) is not true in the case where the medium is bound by a partially reflecting wall. Again, that the concept that Rayleigh radiation pressure depends on the acoustic field only through the energy density of the field is shown to be false. In one instance it is shown to depend also on how the field is maintained, while in another instance it does not appear to depend on the mean energy density of the field at all.

Lesions of ultrasound-induced lung hemorrhage are not consistent with thermal injury

“…Thus, the mechanical mechanism(s) capable of causing such damage are likely related to the stress that focused ultrasound imposes directly on the lung's air-blood barrier such as radiation forces (Chu and Apfel 1982;Elrod et al 1989). We have shown that the histopathologic characteristics of the gross and microscopic lesions of pulsed ultrasound-induced lung hemorrhage are identical in four species (mice, rats, rabbits and pigs) (O'Brien et al 2006) and that hemorrhage in these species occurs at exposure conditions similar to those used for scanning in human beings.…”

Materials Characterization Using Acoustic Nonlinearity Parameters and Harmonic Generation: Effects of Crystalline and Amorphous Structures

“…Brillouin's theory, while predicting the existence of an acoustic radiation stress, does not predict the existence of an acoustic radiation-induced static strain. Gol'dberg [20] argued that the radiation stress is zero and, inferentially, so is the static strain, while Chu and Apfel [24] identified an "acoustic straining" associated with the radiation stress and calculated a resulting "coefficient of acoustic expansion." The conflicting conclusions drawn from the many arguments made regarding, not just the magnitudes of the radiation stress and strain, but the mere existence of such phenomena prompted Beyer [25] to write: "It might be said that (acoustic) radiation pressure is a phenomenon that the observer thinks he understands -for short intervals, and only every now and then."…”

Editors' Choice—The Enhancement of Ion Transport in an Electrochemical Cell Using High Frequency Vibration for the Electropolishing of Copper

“…This drift of mass will dominate the flow up z E-mail: manoro@tx.technion.ac.il to a distance of several wavelengths of sound leakage away from the solid surface, 18,19 which corresponds to the thickness of the viscous layer found in the experiment. Moreover, the similar density of the liquid in the viscous layer to the liquid in the bulk of the electrolyte suggests that acoustic radiation pressure effects 20,21 are not likely to take part in the response of the viscous layer to the vibration in the anode.In this paper we study the mechanisms by which a high frequency vibration in the anode contributes to the transport of ions, to the efficiency enhancement of the polishing process, and to the formation of spatially periodic dents on the anode. Initially, we solve the flow problem, where we employ the steady drift of liquid mass, resulting from the vibration, to calculate the flow in the viscous layer.…”

“…This drift of mass will dominate the flow up z E-mail: manoro@tx.technion.ac.il to a distance of several wavelengths of sound leakage away from the solid surface, 18,19 which corresponds to the thickness of the viscous layer found in the experiment. Moreover, the similar density of the liquid in the viscous layer to the liquid in the bulk of the electrolyte suggests that acoustic radiation pressure effects 20,21 are not likely to take part in the response of the viscous layer to the vibration in the anode.…”