Volume 133, Issue 4, April 2013
Index of content:
- NONLINEAR ACOUSTICS 
133(2013); http://dx.doi.org/10.1121/1.4794395View Description Hide Description
Sound scattering by a system of two counter-rotating vortices (Lamb dipole) is considered, using the effective approach of Pitaevskii [J. Exp. Theor. Phys (USSR) 35, 1271–1275 (1958); Sov. Phys. JETP 85, 888–890 (1959)], based on application of the asymptotic representation of the scattering Green function, the Dirac delta function modeling of the vortex, and the Fourier transformation of the vector of scattering. The sound frequency is supposed to be low. The directivity pattern of the radiation, scattered by the Lamb dipole is obtained. There is no singularity in scattering field in this case as it must be for the vorticity with zero circulation, so the dipole is a more appropriate object for the approximation used.
Efficient finite element modeling of radiation forces on elastic particles of arbitrary size and geometry133(2013); http://dx.doi.org/10.1121/1.4794393View Description Hide Description
A finite element based method is presented for calculating the acoustic radiation force on arbitrarily shaped elastic and fluid particles. Importantly for future applications, this development will permit the modeling of acoustic forces on complex structures such as biological cells, and the interactions between them and other bodies. The model is based on a non-viscous approximation, allowing the results from an efficient, numerical, linear scattering model to provide the basis for the second-order forces. Simulation times are of the order of a few seconds for an axi-symmetric structure. The model is verified against a range of existing analytical solutions (typical accuracy better than 0.1%), including those for cylinders, elastic spheres that are of significant size compared to the acoustic wavelength, and spheroidal particles.
133(2013); http://dx.doi.org/10.1121/1.4794380View Description Hide Description
The interaction of conduction electrons with a longitudinal sound wave propagating in a crystal in a constant magnetic field is investigated. It is shown that the transverse spin current arises when the longitudinal sound wave propagation through the system. The average power absorbed by the spin subsystem of the conduction electrons and the spin-Hall conductivity have a resonant character.
Breakup of finite thickness viscous shell microbubbles by ultrasound: A simplified zero-thickness shell model133(2013); http://dx.doi.org/10.1121/1.4792492View Description Hide Description
A simplified three-dimensional (3-D) zero-thickness shell model was developed to recover the non-spherical response of thick-shelled encapsulated microbubbles subjected to ultrasound excitation. The model was validated by comparison with previously developed models and was then used to study the mechanism of bubble break-up during non-spherical deformations resulting from the presence of a nearby rigid boundary. The effects of the shell thickness and the bubble standoff distance from the solid wall on the bubble break-up were studied parametrically for a fixed insonification frequency and amplitude. A diagram of bubble shapes versus the normalized shell thickness and wall standoff was derived, and the potential bubble shapes at break-up from reentrant jets were categorized resulting in four distinct zones.