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Jan 2010

Volume 127, Issue 1, pp. EL1-611

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Experimental validation of a time domain simulation of high frequency ultrasonic propagation in a suspension of rigid particles

Belfor Galaz, Guillaume Haïat, Romain Berti, Nicolas Taulier, Jean-Jacques Amman, and Wladimir Urbach

J. Acoust. Soc. Am. Volume 127, Issue 1, pp. 148-154 (2010); (7 pages) | Cited 3 times

Online Publication Date: 05 Jan 2010

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Ultrasonic propagation in suspensions of particles is a difficult problem due to the random spatial distribution of the particles. Two-dimensional finite-difference time domain simulations of ultrasonic propagation in suspensions of polystyrene 5.3 μm diameter microdisks are performed at about 50 MHz. The numerical results are compared with the Faran model, considering an isolated microdisk, leading to a maximum difference of 15% between the scattering cross-section values obtained analytically and numerically. Experiments are performed with suspensions in through transmission and backscattering modes. The attenuation coefficient at 50 MHz (α), the ultrasonic velocity (V), and the relative backscattered intensity (IB) are measured for concentrations from 2 to 25 mg/ml, obtained by modifying the number of particles. Each experimental ultrasonic parameter is compared to numerical results obtained by averaging the results derived from 15 spatial distributions of microdisks. α increases with the concentration from 1 to 17 dB/cm. IB increases with concentration from 2 to 16 dB. The variation of V versus concentration is compared with the numerical results, as well as with an effective medium model. A good agreement is found between experimental and numerical results (the larger discrepancy is found for α with a difference lower than 2.1 dB/cm).
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43.35.Bf Ultrasonic velocity, dispersion, scattering, diffraction, and attenuation in liquids, liquid crystals, suspensions, and emulsions
43.20.Hq Velocity and attenuation of acoustic waves
43.20.Px Transient radiation and scattering
43.35.Cg Ultrasonic velocity, dispersion, scattering, diffraction, and attenuation in solids; elastic constants

Efficient frequency-domain finite element modeling of two-dimensional elastodynamic scattering

Paul D. Wilcox and Alexander Velichko

J. Acoust. Soc. Am. Volume 127, Issue 1, pp. 155-165 (2010); (11 pages) | Cited 9 times

Online Publication Date: 05 Jan 2010

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A frequency-domain finite element technique is presented that enables the complete characterization of a finite-sized scatterer using a minimum number of separate model executions and a relatively small spatial modeling domain. The technique is implemented using a commercial finite element package. A certain forcing profile is applied at a set of points surrounding the scatterer to cause a uni-modal plane wave to be incident on the scatterer from a specified direction. The scattered field is recorded and decomposed first into modes and then into far-field scattering coefficients in different directions. The data obtained from the model are represented in a scattering matrix that describes the far-field scattering response for all combinations of incident and scattering angles. The information in the scattering matrix can be efficiently represented in the Fourier domain by another matrix containing a finite number of Fourier coefficients. It is shown how the complete scattering behavior in both the near- and far-field can be extracted from the matrix of Fourier coefficients. Modeling accuracy is examined in various ways, including a comparison with the analytical solution for a circular cavity, and guidelines for the selection of modeling parameters are given.
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43.35.Cg Ultrasonic velocity, dispersion, scattering, diffraction, and attenuation in solids; elastic constants
43.20.Gp Reflection, refraction, diffraction, interference, and scattering of elastic and poroelastic waves

Simplified expressions of the subtracted Kramers–Kronig relations using the expanded forms applied to ultrasonic power-law systems

Joel Mobley

J. Acoust. Soc. Am. Volume 127, Issue 1, pp. 166-173 (2010); (8 pages) | Cited 1 time

Online Publication Date: 05 Jan 2010

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The Kramers–Kronig (KK) relations are a large class of integral transformations that exploit the broad principle of simple causality in order to link the physical properties of matter and materials. In applications to the complex-valued wavenumber for acoustic propagation, the method of subtractions is used to form convergent integral relations between the phase velocity and the attenuation coefficient. When the method of subtractions is applied in the usual manner, the integrands in the relations become unnecessarily complicated. In this work, an expanded form of the subtracted relations is presented, which is essentially a truncated Taylor series expansion of the Hilbert transforms. The implementation of the relations only requires the explicit evaluation of two simply expressed integrals involving the Hilbert transform kernel. These two integrals determine the values of the other terms in the subtracted relations, demonstrating the computational efficiency of the technique. The method is illustrated analytically through its application to power-law attenuation coefficients and its associated dispersion, which are observed in a wide variety of materials. This approach explicitly shows the central role of the Hilbert transform kernel in the KK relations, which can become obscured in other formulations.
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43.35.Cg Ultrasonic velocity, dispersion, scattering, diffraction, and attenuation in solids; elastic constants
43.20.Hq Velocity and attenuation of acoustic waves
43.35.Bf Ultrasonic velocity, dispersion, scattering, diffraction, and attenuation in liquids, liquid crystals, suspensions, and emulsions

Sound velocities and thermodynamic properties of water to 700 MPa and −10 to 100 °C

Steve Vance and J. Michael Brown

J. Acoust. Soc. Am. Volume 127, Issue 1, pp. 174-180 (2010); (7 pages) | Cited 5 times

Online Publication Date: 05 Jan 2010

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Sound velocities in liquid water were measured by the method of impulsive stimulated scattering in a sapphire-windowed high-pressure cell from −10 to 100 °C and pressures as high as 700 MPa. Velocity measurements are compared with previous experimental efforts relative to the International Association for the Properties of Water and Steam (IAPWS-95) formulation for the equations of state. At 0 and −10 °C, sound velocities are in agreement with the one previously published study at sub-zero temperatures to 350 MPa. At ambient and elevated temperatures, differences between the present measurements and IAPWS-95 velocities approach 0.5% near 700 MPa. Inversion of velocity data for density yields results within IAPWS-95 uncertainties, except at the highest temperatures, where elevated sound velocity at high pressure corresponds to as much as −0.2% disagreement with IAPWS-95.
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43.35.Cg Ultrasonic velocity, dispersion, scattering, diffraction, and attenuation in solids; elastic constants
43.30.Bp Normal mode propagation of sound in water
43.20.Hq Velocity and attenuation of acoustic waves
43.20.Ye Measurement methods and instrumentation

Experimental and theoretical study of acoustic waves generated by a laser line pulse in an optically absorptive isotropic cylinder

D. Ségur, A. L. Shuvalov, B. Audoin, and Y. D. Pan

J. Acoust. Soc. Am. Volume 127, Issue 1, pp. 181-185 (2010); (5 pages) | Cited 3 times

Online Publication Date: 05 Jan 2010

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The generation of acoustic waves by a line-focused laser pulse in an optically absorptive cylinder is studied experimentally and theoretically. Experiments are performed on a 5 mm diameter NG5 colored glass rod using Nd:yttrium aluminum garnet laser, which delivers 5 ns pulses. The numerical simulation is based on the semi-analytical model of a radially distributed thermoelastic source, which takes into account penetration of laser energy into the bulk of the sample. Good agreement between the experimental and calculated wave forms is observed. Comparison of these wave forms with an auxiliary simulation, which assumes the model of a dipole source located at the cylinder surface, reveals the effect of optical penetration on the shape of the wave form and also on the relative amplitude of bulk and surface waves.
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43.35.Cg Ultrasonic velocity, dispersion, scattering, diffraction, and attenuation in solids; elastic constants
43.35.Sx Acoustooptical effects, optoacoustics, acoustical visualization, acoustical microscopy, and acoustical holography
43.35.Ud Thermoacoustics, high temperature acoustics, photoacoustic effect

Analytical study of the acoustic field in a spherical resonator for single bubble sonoluminescence

Damián Dellavale, Raúl Urteaga, and Fabián J. Bonetto

J. Acoust. Soc. Am. Volume 127, Issue 1, pp. 186-197 (2010); (12 pages) | Cited 2 times

Online Publication Date: 05 Jan 2010

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The acoustic field in the liquid within a spherical solid shell is calculated. The proposed model takes into account Stoke’s wave equation in the viscous fluid, the membrane theory to describe the solid shell motion and the energy loss through the external couplings of the system. A point source at the resonator center is included to reproduce the acoustic emission of a sonoluminescence bubble. Particular calculations of the resulting acoustic field are performed for viscous liquids of interest in single bubble sonoluminescence. The model reveals that in case of radially symmetric modes of low frequency, the quality factor is mainly determined by the acoustic energy flowing through the mechanical coupling of the resonator. Alternatively, for high frequency modes the quality factor is mainly determined by the viscous dissipation in the liquid. Furthermore, the interaction between the bubble acoustic emission and the resonator modes is analyzed. It was found that the bubble acoustic emission produces local maxima in the resonator response. The calculated amplitudes and relative phases of the harmonics constituting the bubble acoustic environment can be used to improve multi-frequency driving in sonoluminescence.
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43.35.Hl Sonoluminescence

Excitation and focusing of Lamb waves in a multilayered anisotropic plate

Bastien Chapuis, Nicolas Terrien, and Daniel Royer

J. Acoust. Soc. Am. Volume 127, Issue 1, pp. 198-203 (2010); (6 pages) | Cited 6 times

Online Publication Date: 05 Jan 2010

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The radiation of Lamb waves by an axisymmetric source on the surface of an anisotropic plate is investigated. An analytical expression of the Green’s function, valid in the far field domain, is derived. This approximation shows that the anisotropy of the propagation medium induces a focusing of Lamb modes in some directions, which correspond to minima of the slowness. Numerical simulations and experiments demonstrate that for the fundamental A0 and S0 modes, this phenomenon, analog to the phonon focusing effect, can be very strong in materials such as composite fiber-reinforced polymers. This effect due to the plate anisotropy must be correctly taken into account, for example, in order to develop systems for in situ structural health monitoring. The choice of the most appropriate Lamb mode, the excitation frequency, and the design of the array of piezoelectric disks used as transmitters and receivers depends on such considerations.
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43.35.Zc Use of ultrasonics in nondestructive testing, industrial processes, and industrial products
43.20.Mv Waveguides, wave propagation in tubes and ducts
43.35.Cg Ultrasonic velocity, dispersion, scattering, diffraction, and attenuation in solids; elastic constants
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